Why do they still sell cot bumpers and is it safe to use them in playpen instead?

[Warwickmum]

Being first time parents we were a bit gullable in buying two sets of cot bumpers before then finding out that the advice is not to use cot bumpers in the cot (glad we found out the advice for safety's sake but that the shops etc dress up their cots with these things which makes you feel you need them!). My DH asked me the other day when we can put them in the cot (DS now 7mo) and I said that we couldn't as far as I know if we wanted to follow the safety advice. However, I was wondering, does anyone know if it is also regarded as unsafe to put them around the base of the playpen? I only put DS in it in his Galt tyre activity centre at the moment when I nip to loo as don't like to put him in 'loose' with the metal bars if you see what I mean. However, he is starting to get to the point where I think he will pull himself out of the tyre and could bang onto bars anyway.
Thanks in advance for any advice/suggestions.

cot bumpers have been shown to have neither good or bad effects re sids and can be used from birth until your lo gets mobile.

From the SIDS website:

Bumpers: there are cot bumpers in the cot. In the past, there were concerns that bumpers might make babies too hot, increasing the risk of cot death. However, research has shown that they have neither good nor bad effects. Take it out when your baby can get up on her hands and knees so she can?t climb out. Make sure there are no trailing strings or ties.