The problem is spam. The big providers providing hosted emails do a lot of work to make sure the emails people send with them actually end up at the recipients inbox and not in spam quarantine - but that doesn't work if the provider is then used by spammers. So the limits are set to discourage spammers while making most use-cases for email still possible.

If one were to ask me what to do, I'd say emails should cost 0.1 cent each, to be paid to the recipient...