Or, instead of trusting these third parties to hold your funds safely just use a trustless wallet. Much less hassle.
Wasn't BitGo somehow related to the Bitfinex hack that happened a while back? That hack had around $60 million stolen, which means that BitGo likely holds much more funds than the $100M insurance that they've taken out.
Also, it's important to understand that having insurance doesn't mean they will actually redistribute all funds from the insurance (if a claim ever happens) to customers. They will have the final say on who gets reimbursed and who doesn't. Another reason to stick to trustless wallets that only you have access to, of course, with sufficient security.