I guess if i were riding a 60's Triumph, that bled oil from most of the seals, i'd have use for gunk too.
Jap bikes dont need it, the only oil spots are around the chain sprockets and they're easily removed with a rag. I occasionally clean the chain with white spirit.
But hey, i'm not telling you you dont need Muc Off..... its just that i haven't yet found a need for it.
I never had 60'S British bikes only Yamaha, Suzuki and Honda's. To say I never needed Gunk is strange? Maybe modern bikes are different? But I used to cover 40k miles a year as a dispatch rider and they had to have a weekly gunking to remove the road grime, salt and other crap that a bucket of soapy water wouldn't remove. Same with the e mtbs. Getting ground on sheep crap off the frame, wheels and tyres for example, is so much easier with Muc off.