For example it's not difficult to see with this thing how you can end up with arrangements that can only be played on this one modified instrument (which means as a gigging musician you probably need two of them!)

But also you have to spend the time developing the technique to use this thing, which might have impacts on your technique elsewhere.

The Duesenberg Multibender is a great example of this. It's a configurable bridge where separate levers can be configured to bend (usually bend up but with a hefty return spring they can be made to bend down) individual strings by differing amounts, which lets you can achieve voicings that sound like pedal steel instruments. (It's really cool.)

So that is possibly good if you are a pedal steel player but you want a portable lap instrument that has some of those bends for the only couple of pieces where they are needed, or you are a guitarist who has to play a couple of pieces that have pedal-steel bends in them and you don't want to buy a pedal steel.

But it has a cost: configuring the multibender takes time and the levers can only be used with the intervals they were configured for — indeed, if you configure the levers to bend strings down, you are possibly stuck in a single tuning.

It also changes the way musicians play; it's clear that compositions get written around the multibender. So it is, at that point, a somewhat different instrument to learn to really use, which takes time.

There are other ways to approximate some of the bends these levers can do — you can bend the string behind the bar with your finger, you can combine that with sliding the bar up a fret for a shifted pair of notes that match the typical bends (albeit without easy access to unshifted strings), or you can slant the bar, which has its own classic tone. These also need learning, and they have their own limitations (there's kind of only one lap steel capo that can survive string bends and return to tuning)

So for a player, the decision to use, or not use, these extra facilities is a meaningful decision in terms of how they want to sound, how much time they want to spend learning one technique over another, whether they want to compose around those facilities, etc.

(FWIW I would love one and could build a lap steel around one, but I have deliberately chosen to focus my learning attention and playing style on other techniques first)

It's pretty much the same with guitars — a lot of players decide early on that they are going to be fixed-bridge players or whammy bar players. They become quite different instrumentalists as a result.