Until your client tells you that it doesn't work in Edge and you find out it's because every browser has its own styling and they are impossible to change enough to get the really long options to show up correctly.
Then you're stuck with a bugfix's allotment of time to implement an accessible, correctly themed combo box that you should have reached for in the first place, just like what you had to do last week with the native date pickers.
I'd argue that adding complexity from the get-go to ensure that all users have a pleasant experience from the get-go is better than simplicity at the expense of some percentage of users.
I think it's important for web devs to spend more than two seconds to think if the complexity is necessary from the get-go though.
Then you're stuck with a bugfix's allotment of time to implement an accessible, correctly themed combo box that you should have reached for in the first place, just like what you had to do last week with the native date pickers.