I actually keep a stockpile for the same reasons you listed in your post. It's nice to be able to open them all at once when an event is going on that is based on acquiring blueprints, for instance. About every 2 months or so there is one such event, but only every 2-3 of those have a prize worth obtaining.

Furthermore, I think it's nice to save them for future content. When you acquire a new bot, you may want to open 1k crates and get a lot of blueprints all at once (more of an end-game tactic), rather than spending Acorns, which most players simply won't do anyways due to the high cost.

There are also occassionally events that give points for obtaining skins, which is why having fortune tokens in stockpile can be nice.