>>1958738not him but that is a false equivalence.
Firstly, saddles are not leveraged on like handlebars, nor do they affect steering.
You just sit lightly on a saddle.
Secondly the saddle clamp interface of a seatpost is far more robust than that of an adjustable stem.
A seatpost is adjustable to give a superior fit. An adjustable stem is adjustable to give the most extreme riser position possible, which
a: can be done anyway without an adjustable stem
b: is usually a noob fit which is not comfortable for riding any distance or up hills
c: on a cool cruiser, is not cool
Adjustable stems are redundant because stems are already adjustable. The position is going to be limited by your cable length anyway, not the adjustability of your stem, and therefor modifying it to an extreme degree becomes an involved job anyway, more involved than swapping stems or bars would be.
You are correct that an adjustable stem -can- be perfectly adequate, fancy ones do exist, but, they are not the mechanically simple version of themselves, and will be heavier or flexier or both, and more prone to creak or cause problems. Just because you have not encountered this with your tiny experience does not mean it does not exist. You can handwave it away as being 'shitty or broken' stems, but adjustable stems are almost always very cheap and poor quality, because they do not appeal to serious cyclists, so this is not some exception it is a near omnipresent part of their nature.
For example, a single speed bike is the mechanically simpler version of a bicycle, and that does not mean that all bikes must be single speed bikes, a geared bike offers many advantages, it's just about whether you want or need the tradeoffs for complexity.
You can say that the extra utility of an adjustable stem is good and the negatives are negligible, but this thinking will lead you to a bike, through a thousand tiny cuts, which is poor. Bicycles should be optimized at every level.
