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.
The commenter up above is directly referencing where existing 3rd party / escrow services are pretty terrible today and they're certainly not easily accessible to the general public or your average piece of computer code.
A lot of the pre-boom blockchain contract excitement really was as simple as "turn the awful banking middlemen into code so we can get the advantages of them programmatically."
"It's math, bro" isn't actually comforting if the contents of the distributed database are actually in question, perhaps because of mistakes, shenanigans or misbehavior.
No sane risk assessment of "our company depends on this being correct and consistent" is going to sign up for this.
And it's interesting to note that no-one (as far as I'm aware) is doing this. Blockchains have been around for a decade and escrows are still going strong - I don't see any movement to adopt blockchain for this.