Is it necessarily cumbersome or just happens to be like that at the moment?
My intuitive feeling is that it can't be inherently cumbersome; that _must_ be an addressable problem.
Keeping Bitcoin requires you to be really good at both storing a specific string of bits, and also keeping that string of bits secret. Even for a really skilled sysadmin, trusting your life's savings to your own ability to secure and back up a single string doesn't strike me as very wise - compromise or misplacement of digital secrets is almost inevitable.
This is one of the best & simplest arguments I've heard against bitcoin-as-a-mainstream-phenomenon for a long time.
So any setup I would consider safe enough to hold mode than 10 thousand dollars worth of coin is one that is no simpler than an enterprise level security system. It's enormous overhead for any individual. And given how BTC is designed, it's absolutely impossible to delegate most of this work to a third party without opening yourself to more risk.
It's a bit like having your money under a mattress, with the difference being that someone can automate hacking into houses to search under the mattress.
And that doesn't even get into issues like accidents: You also need a backup plan on what to do if you die, or go into a coma. Does anyone get to recover your coins, or are they stuck forever in limbo? It's yet another thing you might want to deal with.
In the regular financial system, all of this stuff is handled for you. If you roll your own, you have to manually build all of this yourself, find who to trust with what... and every single protection you build is also a new attack vector. It sounds rather unsolvable to me.
I am sailing into waters I am not at all familiar with here, but I think the currently-underused multisig/escrow features might offer a solution here. But this really is the limit of my knowledge on bitcoin now.