The problem nowadays, esp since the advent of computers and mobile phones, is that people are obsessed with getting the latest toy. Why this obsession? I think people just want to show off that they own the latest gear.
Of course it is outdated compared to newer cams. But it takes great pictures and works, right? Functions perfectly. You know, when I talk on the phone, somehow, it sounds the same whether I use a Nokia 6150 or the latest Nokia.....
Why does anyone need anything more than a 10D?
If you need to take super wide angle shots, yes, there are limitations as it cannot take the 10-22 lens and third party equivalents.
If you need the speed, then yes, it is a bit slow and the buffer is not great.
If you need lower noise, yes, the newer cams are better.
But if you don't need any of the above, then it is perfectly fit for purpose. Any good photographer can work around the limitations above anyway.
On the plus side, a second hand 10D is fantastic value, considering how much it cost new.