Tug, you've hit on a very interesting topic!
Why do any of us buy the things we do: function, form, aesthetics, character, personal taste, income?
For the sake of my argument, I'd like to stick to Chico's term: 'platform'.
Keeping to the subject of motorcycles, many of us are fortunate enough to own several of them.
The Varadero I bought specifically for its two up touring and luggage carrying capabilities, and I have customised it specifically for that purpose: hard luggage, gel seat, crash bars, hugger, Scottoiler, tall windshield.
The Bobber I bought based mainly upon its character. Yes, I have added leather panniers because I like the thought of having somewhere to stash my jacket and gloves if I stop off on a warm day. Equally, I can pick up a pint or two of milk and the newspaper without having to wear a rucksack (which I hate). I've also added some bling, and performed a few mods just to make it more 'mine'.
I agree with you that some, in my opinion, have been very extravagant with their modifications, but why not! We all justify what we do based upon our very individual desires.
Maybe the Bobber is that ideal platform that allows us all to imbue it with our own identities!
In Roy's case, he only has one bike, so why not transform it to fit all of his requirements? He could have bought a Guzzi California, but he didn't, he wanted a Bobber!