This is the same reason you should (almost) never use broad match keywords in PPC advertising.
Broad match is sort of the default match type in Google AdWords, and Google's own employees often encourage the use of broad match terms, so it's pretty easy to get pushed into using it just by default.
What is broad match
Whenever you add keywords to AdWords or Bing Ads, you set a match type for each keyword. Both platforms have 4 different match types:
- Broad match modifier
If you bid on the broad match term, "shoes," Google will match your ad to anyone searching anything related to shoes.
In this case your ads could show for: boots, high heels, soccer cleats, Christian Louboutin.
This is an important concept for 2 reasons:
- If you don't actually sell those types of shoes, you obviously don't want to be paying for clicks on those searches.
- But even if you do sell them, your performance will suffer if you're sending all those clicks to the same landing page.
Plus, you'll also end up showing for searches that are only tangentially related to selling shoes. For example: socks, Foot Locker, Nike, shoe horn, etc.
Remember, with broad match you're going to get matched with search terms that the algorithms think are even sort of related to shoes. And you'll pay for those clicks, driving up your costs, quite significantly in many cases.
The power of search is that the targeting is so specific. Broad match is, well, too broad.
What's broad match good for?
That doesn't mean you should never use broad match. It does have one worthwhile use: Finding new keyword ideas.
Because broad match will cause Google to match your ad for related searches, you can use it to collect data on search queries you might not have thought of and then use that data to improve your campaigns.
But you have to be careful with this approach. Broad match can eat up a lot of budget and you don't really need to spend a lot to get good data out of it.
So, when used carefully, broad match can be useful for finding new keywords to bid on, but it's not a good idea to rely on broad match to drive leads or sales.