There’s actually no need for most schools to ever buy anything not Cessna if they can.
The wannabe student looks or calls to find out how much it should cost to get a certificate. Then, they shop for the cheapest place to rent a “Cessna”. Not an airplane.
The airlines want pilots they can process into cockpit seat units as simply as possible. That means they want clones who flew Cessnas in school.
The government and the industry creates an environment where school owners are too busy doing anything other than compliance to have time to actually improve their institutions. The FAA abhors change anyways, and improvements other than the most gradual are all suspect. Anyone buying anything new will waste many, many hours dealing with the well intended, but inflexible inspectors who trust no one including other parts of the FAA.
The wannabe pilot, if he or she is wanting to fly for an avocation rather than vocation, is likely nonplussed by the entire flight school experience which was outdated and unattractive decades ago.
We grumpy old old men then point out how useless young people are, get in our decades old vehicles and leave by ground or air (assuming we don’t need to change a spark plug, or something). The young, wealthy, no longer wannabe student gets in their less than ten year old car that’s never had an issue except regular maintenance, will likely save them from most crashes, and drives away to find a different hobby.