OK.
My local club had C172s and other different aircraft. They now have mostly C172s with one or two other aircraft. The reason is this.
Firstly, bear in mind that this is a local club producing primarily middle aged PPLs, not a commercial school.
So the club can present these options.
Would you like to train in Aircraft A, a 4 seater which has a decent range of modern equipment, cruises at a good speed and is comfortable enough to travel around the UK/Ireland in?
Would you like to train in Aircraft B which is more traditional, a lot of people think it is a better training aircraft. It is pretty slow and is only a two seater, it has very basic equipment two. Whenever you have your licence, we can then teach you (conversion or whatever you'd locally call it) to fly the other modern one, we can also teach you how the avionics work in it too.
Most PPLs (of this kind) have the same sort of flying in mind, and it nearly always includes taking family and friends on jaunts around the country. Why would they want to learn in something that will not be fully applicable to what they want to do.
It makes me think of someone who wants to learn to drive to get back and forward to work etc being taught to ride a motorbike first, because there is more to think about and should give you better road sense and appreciation for conditions etc, but it isn't something most people would want to use as a daily commuter.