I'll admit that I kind of enjoyed scales on the piano because I could mindlessly practise them when I was forced to practise, but I feel like there's a point where if you don't know them, you're limiting yourself in all kinds of ways.

Improv and harmonisation benefit from you knowing all the keys on the keyboard inside out. Likewise, if you start going for volume of music you can play, at some point not having those foundations start to limit you.

Anyone can memorise 3 pieces perfectly and over-practice them then ace a test. But what if the spirit of a grade and level represented more than that? My final teacher (who I met long after finishing exams) was very traditional and had a policy that was vaguely "you shouldn't take more than 3-6 months" to prepare for your grade exam. If you can't reach distinction level within that time, you're not ready so you should work more on your actual playing ability and musicianship.

If you're learning like that, scales will be the least of your worries as we worked on so much repertoire that the need for it was self-evident (and well baked into a good routine).

I guess it's a bit like driving - if you memorize a few routes you can probably perform like a real driver, but that's not really the same as being a real driver.

Same for me, I really enjoy playing scales and the like as studying jazz has made the application and benefit of practice a lot more clear.

I did some classical study and grades years ago and remember there being a big disconnect - my teacher just gave me scales and pieces as totally separate entities, and just taught them as things necessary to pass the exam, with no real application or purpose explained to me.

Standard is 2 or 3 octaves, arpeggios, 3rds, 4ths etc ascending only (for some reason), groups of 3 or groups of 4 and the different types of articulation (stoccato, legato, accent on every second, third or fourth note etc).

Honestly that sounds like a lot but all the articulation stuff is the same for every scale and once you get the hang of intervals they are really not hard.

Classical musicians do the above for major, harmonic and melodic minor. Jazzers will typically add the major and melodic minor modes, the whole tone scales (only 2 of those) and the diminished scales. People like me add the harmonic major and harmonic minor modes, the augmented scale and a few other bits and pieces.