You're comparing the end user to the one doing maintenance. Maintaining an email server is way more work than sending snail mail too.

For the end user sending a transaction is quicker and cheaper than getting your lawyers to draft contracts, maintaining your own books, paying an accountant or someone else to manage/balance the books, coordinating a deal/terms with them, etc.

Also there's Proof of Stake which is much more efficient than Proof of Work.