Ideally, BIP70 is actually meant to simplify things and make middleman attacks more difficult to pull off (as each BIP70 URL has an SSL certificate attached to it to make it easier to view who you are sending your coins to), but the problem is that there's lots of opposition towards it like from some wallets, including Blockchain.info and Samourai wallet, and people like you and me can't transact with Bitpay. According to Bitpay's blog
here, the rationale that made them adopt BIP70 included actually the fact that people paid too little or too much, too late, or miner fees resulted in long confirmation times-
I totally agree with that but that dissolves the point of creating a payment gateway.Users want things simplified, they're over complicating it.They can at least have an option to reveal address and recommend a suitable transaction fee.Right now, it is very difficult for an average user with blockchain.info wallet to use their service.Needless to say, people aren't like it at all.It's a potential loss for the services.
Bitpay likely didn't mean anything bad with adopting this, as logically adopting BIP70 would help them become more efficient as a payment processor and possibly reduce staff costs as they'd need less people handling transaction errors, but for whatever reason many wallets still don't support it. It's just a shame those wallets don't support BIP70 URLs, because the regular Bitcoin user might not be as tech savvy as the people on these forums and a nonworking payment URL leaves a bad taste in a newbie's mouth.
You and I can understand the technical implementations of that system but technology is suppose to make stuff easier for noobs.Me being a technical guy had a hard time to send my first payment through BitPay as I had to install Electrum to broadcast the transaction from the URL provided.