Apple are quite happy to trash another company's OS. The Windows iTunes experience was terrible: it ate resources, was opaque in operation, didn't always sync properly and could occasionally wipe your devices. It used to be required for OS updates.
The "nailing shut" is an increasing problem for anyone that believes in a free market in software. Which isn't helped by all these sites shipping value-negative software.
If you have an ssd and more than one Apple device, each device you synch eats up about 10gb of space or more. If you have a spouse with an iPhone in addition to yours, a kid or two with itouches, then that can easily eat up 50+Gb of an ssd drive. This can be a very significant percentage of your drive!! And there's no way to change it to anything by the c drive on windows.
I nearly choked when Steve Jobs described iTunes for Windows as "a glass of water for someone in hell". More like "a bucket of lava for someone somewhere reasonable".
As an anecdote to counter another anecdote, I've never had these problems with Windows iTunes. I've used it since getting the HP branded iPod back in '02 (I think), and my music library has grown into the upper tens of thousands of songs since then.
It's caused me to believe that all these people trashing on iTunes have broken computers, because the software plainly doesn't do half the crap it's accused of doing.
To continue the mostly-irrelevant story time, I've installed it a few times and generally it works OK now but it is still quite slow for what it is. My main computer is no dog either (i7, 16GB RAM, SSD, yadda yadda) and compared to other media player/managers it really is a poor performer.
I can almost understand this on the newer versions since they've made it a sort of one-stop-shop for playing media, managing iOS devices, shopping for media and software, and sorting your content databases.
But the older versions I used back when I had a "classic" iPod were just terrible and all I did with that was load music onto the iPod. I seem to remember installing some custom firmware on the iPod specifically so I could just treat it like an external drive and manage the media on it via Winamp or Mediamonkey or some other program that had no business doing a better job at handling an iPod than something straight from Apple.
Even now I just use it maybe once or twice a year to back up and update my old iPad 2. I haven't found a way to disable all of the various iTunes helper processes that want to run in the background (short of turning them off in services.msc) so it only gets updated and run when absolutely necessary.
Maybe I'm just doing something wrong and it will run better if I open it more often and let it do its thing but there's just a point where it doesn't do anything (other than iOS backups) that I can't do more easily with other software.
...but I also admit that like many things, my previous bad experiences may be causing confirmation bias and leading me to take note of iTunes issues more than I would with other software.
The "nailing shut" is an increasing problem for anyone that believes in a free market in software. Which isn't helped by all these sites shipping value-negative software.