The cost of maintaining that blockchain is insanely high - all those giant "mining" operations. Large numbers of machines have to have a copy of the blockchain and track all updates to keep everybody honest. It takes about half an hour before a data item can be considered solidly committed. Even for Bitcoin itself, this is is an operational headache.
If all you need is a certified timestamp on something, several European certificate authorities run free trusted timestamping services. You send in a secure hash of something, they add a timestamp, sign that, and send back a reply.