Makes things easier for when you're gone. You'll probably have some next of kin, even if you're on bad terms with them.
If you die without a will, the state ends up determining what happens with your possessions. That usually means that they'll go down a list of relatives and ask them "hey, this person died, do you want to inherit their belongings". If they find absolutely nobody (this happens a lot with people that die with a lot of debt, since you also inherit the debt), the will instead falls to the state.
The order makes some sense (first is spouse, then kids, then siblings, then direct family and finally extended family), but it's of course something left up to the present state of the law and depending on how that might change, something could occur you're not happy with.
One specific example of this (albeit not for your case) is in the event you're gay; gay people often had to prepare their will specifically because the state wouldn't acknowledge them as the spouse (this was even with the "civil arrangements"), so the state would just skip over their spouse for inheritance and relinquish stuff to their family instead.
This doesn't apply of course if you're not married, but it's one simple example in how that default order might have some asterisks that are easily avoidable if you just have a will.
Basically it's useful to have one to avoid a lot of complications in the event of an untimely death (which can happen for all sorts of reasons).