Why use bedding?

So I recently had a sick little girl (Skittles), after a couple kinds of anti biotics and a pain killer she is back to her normal grumpy self. While at the vet she told me to stop using the fleece liners for a bit because she noticed Skittles had blood in her urine. The liners were hiding this and I needed to keep an eye on her urine to help monitor if she was getting better. Now that she is better it got me thinking what is the purpose of fleece liners anyhow? I did it because that is what you are supposed to do and I never questioned it. She still has her beloved fabric bags to snuggle in, but is it really that bad to not use liners? The base of her cage hes a texture (very slight) to it and I'm wondering if maybe it will help keep her nails trimmed if she's not always walking on soft stuff. (nail cutting time is very stressful for everyone involved)

I would think fleece would be fine but you would want white so you could see if she had blood in her urine, white fleece should be better then bedding I would think

Typically, you can detect things like blood much better using fleece (provided it is a light colored fleece - like white or cream) than you could using bedding such as shavings, Carefresh, Yesterday's News, etc... Bedding that comes in small particles will hide things like urine, blood, and poop. With fleece, it's sitting right there for you to see.

I wouldn't leave her on the bare cage floor without the fleece. Hedgies are rather sensitive to temperature changes. Having bedding helps insulate them from that. Also, it wouldn't really help with her nail situation. Hedgie nails grow out before they start curling down toward the ground. By the time they reached the ground and came in contact with a rough surface, they'd already be way too long and causing hedgie discomfort when walking. Also... think about how soft hedgies' feet are. If you have a hedgie walking on a surface that's rough enough to grind down nails, it's going to wear bloody holes in the bottom of those pudgy little feet.