I ran an NZXT Kraken X61 with Cam for better part of 7 years before the fans gave out on me, (yes, the fans lol). There was only 1 issue I had with Cam and that was the updates. Occasionally I'd actually have to open it up and redo the settings. It wasn't a program I ever really used, just had running. Made a Windows Task to bypass the UAE and set it for Silent mode. Done, didn't mess with it again.
Others have issues with Cam for 2 major reasons. First, it's a deep diver, it gets its nose everywhere in the system, it really should considering all that it does. Second it reports your usage to nzxt, they like to keep tabs on what pc's are running what cooler and at what temps, for how long. Nothing personal, but some take issue with it. The excuse is reasonable, they wanna know how their stuff is performing and not relying on Amazon reviews.
Most 120mm aios run @ 140-150w class cooler. A Corsair H60 has almost identical performance to a CM Hyper212 Evo in every department. That's the kicker, why spend (at the time) $90 for an aio that does the exact same job, exactly the same, as a $30 aircooler, and will only last @ 5-6 years.
Simple answer, because I want to. I had a Corsair H55, loved that little thing, ran great and quiet, sold it when I sold the pc after 5 years of use. Most ppl update, upgrade, change coolers with every pc purchase, very few actually re-use older coolers unless they went overboard on big air to start with. Anyone upgrading from an old 4760k to a 12700k isn't going to reuse their $30 CM again. So longetivity and reuse forever tends to become a moot point unless you have a D15 or BQ DRP4 etc.
AIO vs Air is a personal decision. There's benefits and drawbacks to both designs. Spend $150 for an RGB aio, that has 3x RGB fans included, or spend $90 for a D15 and then another $100 for 3x RGB fans to fill up the top vents. Air is cheaper, but most tend to forget the extra expense of the fans for airflow reasons. But thats aesthetics. Air can cost more, overall, depends on how you want your pc to look. Personal taste.