I think the problem is that most of those shows the networks cancel, they cancel because they're not good. I'm sure there are exceptions, like Firefly, but for the most part even the better TV shows aren't very good, IMO.
Just because there are some really bad shows that get cancelled does not mean all of them are bad. There are a lot of good shows that get cancelled mixed in with many more that are not.
A lot of tv shows on the major networks get cancelled because there is a finite number of prime time slots and a X viewers in one time slot on one night for a tv show on one tv network might be small while on another would be their top show.
That's just it though, most people these days do not start watching new shows week to week unless its a proven IP brand or the network is spending a massive amount of money on advertising promoting it.
Most people think, "well, if it's good, it will last and I will watch it later" so fewer people watch. By not watching because it's inconvenient to watch weekly or because there are a LOT of other options available at any given moment, it creates the illusion that the show is not popular or good enough for more seasons.
Quite honestly, the only scripted show I have ever watched that would have been worth watching weekly was Game of Thrones and I didn't even do that because to me that's like reading a 100-chapter book one chapter per week when you have several other complete books or books with at least complete multi-chapter story lines you can read right now instead.
As I said, older people are conditioned to weekly episodic content and have more consistent life styles and viewing habits.
I don't see why your preferences are more important than providing options to everyone though. Your way limits people while mine provides everyone an option to consume media the way they want.
At least with entire seasons released, you can still watch them any way you want to watch them. No one is forcing you to watch them all at once. You could even watch a 12-episode season show one show per month and likely never have to skip a month as the next season would start around the time you finish the last episode of the current season.
For me, I watch things the way that fits my schedule and my time. Weekly-based shows are nothing more than a few months of trailers for me. Once the show's season ends and they announce a renewal, I watch the entire season as my schedule allows which may be in a weekend or over a couple of weeks.
That said, I usually don't watch most weekly-based shows until they have been out multiple seasons these days simply because again, there are so many other things to do and watch that I don't have to waste my time with tv networks that dictate and cater to a dying demographic of viewers.