It's psychological, right? But it's also supportive: if you have access to a credit line, you're less likely to feel the need to get liquid by selling something that you're not quite ready to sell. Selling stuff you don't want to sell is a good way for crunches to snowball, since then others who are holding that thing see the price go down and are similarly pressured to sell.
So why not create something out of thin air and let people borrow it to keep them from selling off other things?
Sounds good to me.
/jordan