If there was only a single choice for advertisers to place a completely static banner on the page, they would still be happy. As long as no other advertiser had more capabilities.
Restrict them all and the money would still flow as the ads would increase sales just as much.
It boils down to greed. Targeted ads are proven to have larger profits, which increases the more precise the targeting is.
No advertiser wants to go back to dumb ad campaigns like they used to run on traditional media, simply because they're far less profitable.
Which is why they're concerned about the restricted and more general profiles the Topics API will give them. They want even more granular topics[1], and Google can do this at any point once the controversy has died down, and this feature gains traction.
Make no mistake that if this turns out to be less profitable, many advertisers will still resort to cookie tracking, fingerprinting, and any other shady mechanism, as long as the browser and lack of regulation allow them to do so.
Restrict them all and the money would still flow as the ads would increase sales just as much.