Google would obviously start losing money though if people perceived Gmail as easy to hack.
It's called externalizing your costs, and Google is exceptionally good at it.
They are very aggressive about fixing TLS/SSL-related issues (finding and fixing vulnerabilities, deprecating old ciphers, promoting new stuff like cert pinning and HSTS, lowering SERPs in Google for non-https websites; they've also put in place means to detect and report fraudulent HTTPS certs, and many more).
Many of the top security researchers work for Google, and many of them even not on things directly related for Google's daily businesses.
If I'd have to say about some bigcorp that they don't care about security, Google would be the last on this list.
Google customer support is totally another pair of shoes though.
Pair of shoes! Nice. I tend to say "why the face" a lot in our internal chat at work. Now I have another one (POS)
No, they've built their model on the fact that for the vast majority of their users this will never be an issue. Maybe a celebrity, maybe an important target but the average user, never going to matter.
Email is the gateway to almost everything else. It's used for account recovery as well as (wrongly) passwords and other sensitive information. Google Drive and docs would also be compromised.
It's actually a bigger issue that you would think.
[1] So we have two probabilities at work.