I think the reason is Morgans are already heavily customised to each owner, you very rarely see two the same with many subtle differences in spec, colour and accessories - with the phelora of options available most people are happy with their chosen spec.
Its also worth mentioning that car modification is very much dying over here, the days of Max Power are long gone and the amount of modified cars is decreasing constantly - the availability of "M", "AMG" and "RS" styling on standard models is surely partly responsible also. For this reason most modifications are seen as a bit "boy racer" or "chav" and this makes them less desirable.
As such originality is looked on more fondly, and with classic car prices on the up this is also securing this trend.
With regards to hot rodding and that sort of look, its always been a niche with certain cars - and Morgan's don't fill the bill.
All IMO of course..
