For holding BTC use a desktop wallet or blockchain wallet. They are safe instead of Coinbase.
Many of the wallets are seems operating same like coinbase.
I too know that coinbase is based with exchange still you find the wallet on various platform with better than other wallet specifications.
Then read their security concerns and norms they follow to secure their wallet users.
without even thinking that Coinbase itself is an exchange site and which do have a certain wallet too but as being said you wont
really have your own private key just like on any exchange too. You can use up as a wallet but the risk on losing when theres a problem is
high.