This could be for several reasons like it takes up too much space, is redundant since a link is provided, or it could be that the coupon site owner wants to get paid for their work of finding the coupons for you.   Also, it could mean that the website or blog owner is just giving you a free link to freebies and/or coupons.  Again, the manufacturing company absorbs the cost of advertising, and the consumer should not pay for any coupons or freebies.
     The coupon site owners work to keep their website filled with up-to-date coupons for you to use.  It is an incentive for them to work to make sure you are getting the coupons you want, thus, insuring them a profit.
Groceries, Traveling, Clothes, Websites, Electronics, Arts & Crafts, FREEBIES
     I hope you find many coupons to save money.
    Going straight to the company for a coupon is direct.  A

direct product (manufacturer) link

is a link to the company that actually makes the product--from another website.  Some companies with numerous products engage the services of coupon websites that collect information and/or display the company's coupons.  There are many of these coupon websites that act as a "middleman" for the large companies.  They are paid for this service, and the costs are to the company, not the consumer.
      Some coupon collectors may be reluctant to follow links for coupons and freebies because they sometimes get transferred to other non-related links.  Most consumers just want the coupon or freebie, and don't want to spend the time sorting through unrelated coupons, being transferred and required to fill out multiple forms handled by a middeman.
     Other collectors may like personal blogs that trade specific coupons.   The costs to the consumer on any coupon website is the same since the company absorbs any coupon marketing fees.   Also, you might notice that the same coupons appear in some form or another on many different websites.
     Most

commercial coupon websites

simply display a picture of the product, a link to follow or a coupon facsimile (looks like a printed coupon).  Some are actually direct links, while others are coded website links that permit the website owners to get credit (paid) from the product manufacturer.  In any case, you should be able to identify a manufacturer's site, if you look at the links.
     When you visit a coupon website, look at the display u-r-l at the bottom of the coupon advertisements.  For example, if you are looking for a cereal coupon, you can link directly to a specific cereal manufacturer's website rather than looking through "related" ads for "toothpaste" or other things that may be made by the same company--but you aren't looking for at this time!  If it says "cereal" on the title (which is a link to the company) and lists a familiar cereal company on the url, you probably have a direct link.

Direct Product (manufacturer) Coupons/Links

the company in your web browser, go to their website, and hope that they have a coupon offer available.  Not every company has coupons, and some companies that offer coupons may have them for a limited time.  You can waste time searching each company's website for coupons that they may or may not have!
Cheerios
     If the url, in this example, www.generalmills.com, matches the top description, in this example Cheerios Cereal, it is probably a direct manufacturer link.  The area highlighted in red (color added for illustration) is where to look.  The area in blue in this example, is the link for the product that will take you to the website.

Sometimes the URL is omitted or just not provided to the consumer.

Sample
www.EducationDx.com
How to read ad codes and get the coupons you want!
An educated consumer is a smart consumer!
COUPONS:   DIRECT PRODUCT LINKS
Coupon
This is a FREE information site!
Part of EdDx Educational Series
EducationDx
    ©2015
Cheerios Cereal
Cheerios can help
lower cholesterol
www.generalmills.com

Tip:  Turn on your web browser's javascript.   If you are serious about finding coupons/freebies, some websites have free coupons/ads, but you need to have your javascript turned on to see the ads (you have it--this is not Java)!  Someone (another user ???) may have purposely or inadvertently disabled javascript.  Also, some websites may require cookies so that the website owner can get credit for your visit.
(If javascript is disabled in your browser, you won't see this message.)
(It's so easy!)
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How to turn on javascript>>>
     If possible, some coupon collectors would rather deal directly with the company that makes the product rather than using for-profit commercial coupon websites.  Some people prefer personal coupon websites or blogs that focus on educating consumers and may have direct links and/or other optional sponsored advertisements.  These websites/blogs are for people who are serious about saving money, are willing to read short articles on how to do it, and want to grab some coupons or freebies while doing it! 
    If you are looking for coupons for a particular product, you could simply type the name of