What reason?I love Carvin but there is a reason the audio side went out of business for a while.
I've never experienced anything but awesome from any of their amps. I've bought only used amps and speakers from craigslist, lots of carvin stuff over the years due to nice low used prices, and they have always worked flawlessly. I've opened them up (I always do with my gear - I prefer first hand information), and always been very pleased with the builds.
If it's sound quality, well sure, for guitar amps and such there is a unique tone for many manufacturer's designs... and I totally can understand Carvin being a bad match for some guitarists/bassists looking for certain tones - just like with any other brand. Their PA stuff was amazing, but then I only owned a pretty high end pair of mains from them and a power amp - so they ought to have been great, and they were.
But then, behringer makes some pretty amazing sounding stuff too LoL...
Anyhow, I'm honestly just trying to learn the reason behind your statement. I don't disbelieve you - I just have only my personal experience with their products.