Probably hurt revenue ;)
- hard limits caused downtime more often than they prevent these blog posts
- hard limits were inconsistently enforced, even within GAE
- platform wide quota notifications were implemented (reached "GA"), leaving the question of "how a developer wants to handle this" to the developer, not the platform
- maintenance burden
The "I bankrupted my startup by running tests in an infinite loop" blog posts happen ~once a year, while the number of customers (including internal teams!) who inadvertently went down because of this quota was staggering. I feel like I used to see one a week, at least. Most often someone on the team was like "oh I'm going to turn this down to zero because we don't want to spend any money during development", never told anyone, and then they go live and they forgot to turn the knob back up (or didn't properly estimate traffic/costs and set it too low).
I can tell you it hurts revenue a lot more when a large customer goes down for 15 minutes due to quota issues and their usage drops to zero (both in terms of revenue and customer credibility) vs when tiny developer accidentally blows through 10k in a month and we refund it (since, obviously, the providers cost is a lot less than that).
When I also think of the fact that Google tied it to requiring a credit card for almost every single transaction even if it is free gives the impression that it is for financial purposes (aka a way to get more out of developers or those who might be free-loading on the free tier of App Engine)