It discourages experimentation and use. It also adds significant mental overhead when it comes to using something. One can imagine this mental overhead when using Canva or Photoshop. But if evrry app was like that the complexity would rise exponentially.
Metering leads to reaching local optimal states at best, and makes it very difficult to reach a global optimal state.
There is very little marginal cost when software is concerned so metering isn’t even reflective of the costs of using a product.
However, this isn’t currently true of AI. AI has significant marginal costs so metering probably better aligns with the expenses, but metering is so bad for other reasons that most companies are choosing to forgo the “reflective of costs” benefit and just charge flat prices anyways.