TDIL Coinbase insures money lost from physical security, cyber attacks, and employee theft. they keep 98% of their funds offline. So back to my original point, is it really that important to keep your money off exchanges if they offer insurance and you personally make sure that your account isnt vulnerable to phone attacks? https://support.coinbase.com/customer/portal/articles/1662379-how-is-coinbase-insured-
Any exchange can be hacked, it has happened multiple times in the past. However, personally I think coinbase is one of the most secure exchanges available currently.