If there was an incentive to do so there would be.

Alphabet doesn’t have real competition. If they start getting some they will be motivated to improve. Amazon the same way. You order crap from them and they still make their money. Social media the same way, there is just no particular reason for them to anything about bots when bots don’t impact ad numbers.

The corporation I work for has a captcha on the website to do pretty much anything useful. We have an incentive to not have bots.