Imagine there's an exam in allotmenteering you could take. At the simplest level, you would have some elementary horticultural questions: differentiate between peas and potatoes from their foliage, say. A trained examiner with a clipboard would watch you digging and raking, pushing a barrow-full of oomska around an obstacle course, and make an assessment of your ability.
If anyone suggested I take such an exam, I'd respond with what I can only describe as a scornful guffaw. Gardening is my hobby. I've been doing it on-and-off since childhood. Sod off.
Learning to play the piano is a hobby, too. Admittedly, there aren't too many parallels between the 2 activities, but they have this in common: I do them in my free time, with no thought of reward or praise or anything else but enjoying the doing of them, and aware that doing them is part of a process.
By that I mean, the allotment will look different and be more productive, some years from now; and my piano playing will feature more skill and a modest but growing repertoire of learned pieces, also some years from now.
Bugger the ABRSM exams. I came to this conclusion when I realised that trying to play Dance of the Hours just so was becoming tiresome. I don't have as much free time as I'd like, so it seems perverse to fill that time with tiresomeness. ABRSM grades structure is fine, so far as it goes.
Just for the hell of it, I bought a Grade 5 scales and arpeggios book from the Dennistoun Baptist Church charity shop the other day, and I'm having great fun with it. I've dug out a book of Grade 1 Pieces and I'm in the middle of learning a simple version of Peggy Sue. Now I practise more than I have done in months, and get onto the piano stool with no sense of duty but, instead, literally, with a song in my heart.