How about because they fly? ... and cheaply!
Javelin,
I own a VP2, it's not sexy, it's not fast, and it climbs like a brick. BUT! it cost me £2500, It operates from a farmstrip for next to nothing and I can fly whenever I like, weather permitting. It will take off and land from from my 350m strip (hedge to hedge), which with 30 foot hedges either end is more than many aircraft. It flies at 70mph which isn't fast but is equal to "sexier" aeroplanes like J3 Cubs. It's open cockpit and a taildragger, which in my book equals fun, plus it's very easy to maintain. The Luton Minor falls into the same category but has the bonus of having delightful flying characteristics ( I was in a group operating G-BBCY ) ... so I ask you why wouldn't you want to own one of these types of aircraft?
For how much they cost to operate ... (in my case about £20/hr all in!) you can afford to treat them like a sports car sitting in the garage to use at the weekend! They might be impractical for going places, but is that all you fly for? After all, if you were honest, apart from summertime or if you're IR equipped, no aeroplane operated at PPL level is practical for travel compared to a car anyway!
Zlin ...
If a bathtub with a door was certified as airworthy, I'd want to fly it for the challenge ... but then I'm very slightly nuts. The Luton Minor is far far more civilised!
IM