Maybe - but in many countries it isn't. In my European country, calling a cab means always talking to the operator (often after 2m ringing) and then waiting 10-30m. Around 10% of the time it never comes, so you'll have to call again. When it finally does, your reward is paying an extra fee for having called.
Then there are the zones; your home is a bit outside the city? The meter will be running - at an increased rate! - before the car even arrives.
Never had that problem here in Edinburgh - been using the same cab company for years (both personal and business). They have an app or an IVR system or an operator.
Never had a missed cab, cars are always very clean and drivers good. I honestly can't think of a single problem I've had with them in what must be 15+ years of regular use.
Then there are the zones; your home is a bit outside the city? The meter will be running - at an increased rate! - before the car even arrives.