I used to work on this stuff, years ago. It seems arbitrary and harsh but makes sense in cold engineering terms.
The purpose of an account lockout is either:
1. Stop a clear abuser from trashing the network, e.g. by sending spam that will get Google IPs blacklisted (yes this happens, there are no special breaks for Google).
2. Challenge an account in such a way that false positives have a chance to 'clear their name' by doing things that serial abusers have difficulty with, like passing phone verification or in the good old days, solving CAPTCHAs.
Virtually all responses to service violations in the consumer world are (2). They're automated, people pass the challenge when they log in and never think about it again so you just don't hear about it.
Corporate services pose special problems. Companies expect to be able to automatically create large numbers of accounts using APIs, which is something not allowed for consumer accounts. The latter are carefully monitored, throttled, and ultimately the services may just refuse to let you create an account. Tough cookies. That doesn't work for GSuite domains where the administration is devolved, so what happens when spammers notice this and create such domains then add lots of users at once? Yes they're meant to pay, but some abusers can get past CC fraud checks and other mechanisms that would otherwise make this approach too expensive.
Unfortunately the rapid, automated nature of abuse means that the response also has to be rapid and automated. It's not as easy as saying, hmm, foobar.com looks suspicious, let's get a trained expert to mount an investigation. By the time the specialist has woken up and got into the office the attack is over already and you sent 10 million spams or hosted 50,000 phishing sites. That's the flip side of very scalable systems with convenient signup, in which the admins don't suffer any consequences of abuse they proxy or allow (i.e. when you buy GSuite part of what you're buying is Google's spam reputation). That's also why these stories so often resolve with an ending like "A googler got in touch and we're back in now". This creates the impression that the only way to get support is to flag it up on Hacker News or Twitter. That's sometimes true for consumer services where getting people to look at your case is harder but for companies with support contracts, it's often just due to the time lag involved between someone doing a manual investigation and resolving it.