A very good reason will be the amount it costs to keep one of these in good condition and on the road. Compare the running costs for a classic car to those for a 1.0 Saxo or other small hatch. If these were such a great idea then don't you think everyone would be running about in a nice looking classic instead of spending money on new cars?
You're still going to have reliability issues, it's an old car, things WILL go wrong with even a mint condition one. This isn't speculation, I'm speaking from experience here (of classics in general).
What exactly did you get an insurance quote for and how much did it come in at? All your posts seem to lack any detail besides "I R WANT THIS CAR NAOW".
I know it won't be as reliable, but there a lot simpler to work on, and like I said I have a very kind mate (well he's actually my dad's mate) who would almost certainly help out (he has a few classics he services himself and stuff).
I have been quoted £1600 TPFT with Adrian Flux