Stan Brown wrote
Bert Hyman wrote

There's also a chance that the screws you're buying aren't any good.
A lot of the stuff that you find in chain hardware stores is real crap.

Thanks for the suggestion, but these aren't screws I'm buying.
They're screws that come with the towel rack or window blinds or
shelf or whatever.

Not that that necessarily invalidates your point, but I'd think that
the manufacturer of something to be mounted would provide decent
mounting screws or none at all.

Or they provide what they believe are useful and you are
welcome to use something different if you dont agree with that.

Most of us would rather have the screws included so we can use them if
we decide they are satisfactory and can bin them if we decide they arent.