Microcars certainly exist but I take your statement and would refine it to suggest that its scope has been stretched by folk to include additional machinery that used not to be included in the arena as you suggest. This has resulted in an effort to increase values but also to belong or to take part in a scene where the choice original cars are out of the pocket of those attempting to join in. Of course the edges are blurred, just as are Cyclecars. The Cyclecar seems to have a end date as modern cyclecars are not called such but appear as Microcars, Velorex, French Bel Car thing for instance. So there is a date issue to add to the debate.
Reliants were not ever included as a Microcar, but then neither were Fiat 500 originally, which clearly tick all the boxes. There seems to be something about sales success which disbarred certain cars yet the clear minimalist successes like the Goggomobil have always been Microcars and might beat the total of all Reliants made at 278,000 odd units. Those 'non-microcars' found themselves grouped as Lightcars. The Lightcars, NSU, Trabbi, BMW 700 etc. are the ones that ended up being marginalised and ignored over time and that is why those that have no great club following knock at the Microcar scene's door being cheap enough for less affluent MIcrocar enthusiasts to buy and use, as they keep up with traffic better. Sadly, for me, that does not make them MIcrocars but that's not to say I do not want them turning up.
I do not understand why Reliant owners seem to have a chip on the shoulder about Microcars. Reliants have had a club for years. I can remember a time when many bikers had a Roly for the winter. Roly's were better in use than most of the Microcars and that was why they saw them off and ended up as the niche Trike market. I can only assume there is some sort of issue over the fact that Microcars have become collectable and in some cases valuable whereas most Rolys have not really been recognised as a desirable item. That is not helped by the still common activity of breaking up every other car that appears for parts and historically not reacting when caches of cars came up needing rescue like the 10 Groomfondle cars. If a group do not invest in their marque it can be no surprise if there is not a dynamic following resultant, though the one does not always follow the other of course. I was very disappointed at the turnout of Reliants at the National Microcar Rally. I was hoping to learn something and identify what my Rolys are and need but I cannot say I was motivated. I now know of a load of spares, not sure I want to buy them up if Reliant owners remain as negative as they were when I cleared Groomfondle. The damn cars were free and no one wanted them! How can you sell good spares to peeps like that. Its as daft as the Bond owner who towed a trailer from Brum all the way up to Rotherham to refuse a free Bond MInicar and moan about his costs of trip! The answer is of course, export it to folk who do want to spend money - like Holland, Germany and America. That will lead to the values going up like Microcars and put them on a par. The only trouble is like many micronauts you risk no longer being able to afford the car to really join in. There is no easy answer save that it is fun to be in when the cars are not interesting, ride the rise where people are having fun with the cars and leave when they become to valuable to be used and collectors dominate. Surely Rolys are on the rise now. Is it time to get on board as the pendulum swings away from Microcars as active machinery?