[mriou]

They have. But only if you're on node.js and you need to run bitcoind yourself. Which means maintaining it, backups, restart scripts, etc. Building the transaction using BitCore isn't really simpler either (see the sample https://github.com/bitpay/bitcore/blob/master/examples/Creat...).

So using BlockCypher's API to do that is much more portable (you have ECDSA signature libs in most PLs) and avoids all the hassles of additional infrastructure.