DSLR cameras are based on the 35mm film size.
The lower cost DSLR camera have a smaller image sensor than 35mm but compared to the non DSLR cameras it is very big.
A larger target inside the camera means a larger diameter lens. And that means a lot more weight.
You can get lenses that are comparable to a 10X optical zoom. Most will come with a tripod mount on the lens to support the weight.
But that does not keep some people from using long zooms on DSLR cameras.
Check this link:
I'm really ignorant about optics. With that said, I'm wondering why the lenses for SLR cameras (both film and digital) seem to not have the same zoom capability you can easily find in many video cameras and less costly digital still cameras.
If I had to guess, I'd say it may be because the lenses would be prohibitively large for the amount of light the SLR lenses ''pull in'' or because of the size of the film-plane image they yield.
Am I close? I hope there's an optics-savvy forum reader who can answer.