Because, according to the old paradigm, part of using email systems was the chore of deleting old messages. Much like it's perfectly natural to a lot of people to find a company's website, download a setup program and run it instead of running a package manager.
Maybe it's just me, but I still have to delete messages. Otherwise a bunch of crap I no longer care about gets returned in GMail's search, completely defeating the purpose of having a search-driven interface.
I find I'm unable to determine whether a message is crap I'll never care about again or not.
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).
I guess just about everything Google will classify as "bulk" I'll never need again. The Groupon deal that expired yesterday isn't something I'm going to need to access 2 years from now. Maybe those monit alerts I will, but in all likelihood not. Things like that. But they usually end up having just enough terms to throw off GMail's already terrible search making it hard to find content I really care about.
> Otherwise a bunch of crap I no longer care about gets returned in GMail's search
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.
