Agreed. I definitely have more than 1GB of email, but asking one would need/use that amount of storage is a perfectly legit question.
Often I can't think of a reason I'd possibly ever use a message again, and lo and behold there's some strange reason I want to refer back to it 2 years later (e.g., figuring out my start date for an old job on a new application ... weird little cases like that).
It may be a language issue or a query-building issue, but I feel no difficulty searching through my gmail mailboxes. I often adopt an iterative approach where I build up my query by watching what gets returned.