Yes I set bleachbit to run after boot when I turn it on every day.
Not because I care about any emails. It the crazy 100MB of crap browsers leave behind from the previous day. I don't bother to shred, just want to free the space. I guess it improves performance too.
Yes it's probably pointless when you have multi-GB of space. It is because I remember HP7920 disc drives the size of a dishwashers with 50MB disc platters.