Operating in high speed mode is something best learnt when the situation is ideal - CAVOK, not much traffic, ATC don't mind etc etc. It does require practise, in order to then be consistent in more difficult situations. I think that it then remains as another string in your bow should the situation arise.
As an example, you're kept high by ATC. You can use high speed to lose excess height when cleared down. You can then get in a mess if you're not practised, or it can be easy if you're practised.
The benefits of it's use in everyday operations (short haul) are difficult to quantify in cost versus time-saving terms - swings and roundabouts. The time saving on it's own is usually not worth the effort. If your Company SOP says high speed is non-standard, then there's your answer for everyday ops. and it's also your answer for any colleague who regularly ignores it.