I wonder why Microsoft doesn’t do the same: let people use the Bing API for free while injecting Microsoft Advertising ads into the results.. as opposed to not

I wonder why Microsoft doesn’t do the same: let people use the Bing API for free while injecting Microsoft Advertising ads into the results.. as opposed to not even allowing people to apply for their ad network which makes it near impossible to build a search engine using Bing (since the pricing is $3-7 / 1000 queries).