They'll have to provide proof of death, which every other company has to deal with when people die.
What's one more thing that crappy family is going to do, not like they're going to only fight over the stream account and not fight over the house, land, or cash.
I'm going to be a little snarky here and say, "Won't somebody think of the corporations!" Having to do some extra work isn't going to bring down a billion dollar company.
Who cares if it's not a simple solution? A legal solution should be provided since we as gamers have paid for these games and we should have a avenue to pass them to our surviving kin or whoever we want.
Most companies are not international, and don't have to deal with verifying the death certificates from 100+ countries.
The challenge is that dividing it up would add overhead to Steam support, especially if the estate does try to break up an account into games. Not to mention that there's really no "cash value" on digital games, since there are things like sales, giveaways, bundles, etc.
It obviously won't bring them down, but assuming extra work and liability isn't something they'd do our of the goodness of their hearts.
We pay to license Steam games and put them in our Steam libraries. This isn't a new idea...it was a criticism of Steam when it was new, and it was why there was so much pushback. If you're buying expensive brand-new games on Steam rather than on a DRM platform (or waiting until the cost lowers enough to be worth getting only a license), then you've been using Steam wrong.
I'm not even defending Steam here. If you want DRM-free games, buy from GOG. Steam has more games, and sometimes lower prices...but you're not buying a game that you own. It was never a secret. Hence why they marketed it as a Steam Library. You can use whatever you want in the library, but you own none of it.
A lot of the problems are already solved by probate/estate/etc.
Like, if you had property at a bank, you'd need a death certificate which you'll have requested tons of if someone you loved died... along with potentially some sort of proof that you were the rightful heir (Worst case, you'd establish this through probate, likely going to end up being a simple document). This would be more overhead for steam, but usually not complicated documents once everything is settled. As for splitting up the account, your steam account would probably be classified as a singular item and any attempts to break it up in a will would likely just end up being void.
OTOH, Steam is an international company, and there are different standards and such for death certificates across the world. So Steam would have to have some expertise in verifying death certificates from any country they operate in.
Increasing overhead and liability when they'd probably earn very little good will is usually not the best business strategy. I don't think they'd do it unless they were legally compelled to.