Riddle me this science people - platelet donation

I was dinking around online, the UK version of the bloodmobile is in my corner of Essex next week. In the US I was a regular blood donor. In Germany I donated three times through the on-site company bloodmobile visit, but found the officious brute of a bloodmobile doctor to be obnoxious on the third visit and thereby stopped. (She chewed me out that I did not have fluent German and she did not have time to talk slow German and on and on.) As it is an American company with many nationalities who do not speak German, I pointed out that they shouldn't put the posters up in English then. (The rest of the staff was very nice as they find her pompous as well, but I really didn't have the energy for such events in Germany after a while.)

So onward...I was looking online at the UK blood donation rules, having previously been a UK blood donor when I last lived here. I was specifically interested in donating platelets. I had looked into this one of my home visits to Philly after the above Germany debacle, but having lived in the UK during the Mad Cow years, I was ineligible to even be a blood donor anymore. I was interviewed by the platelet people by phone and then invited in but my travel history then disqualified me.

I was looking at the UK platelet donation site, apparently I'm already disqualified from the get go, due to being female. Really now. Off I went to google to figure this one out. I stumbled across platelet donation in Singapore which seems to shed some light on this mystery to me, although they only 'prefer' males as oppose to 'require' males like the UK. Funny the US doesn't set gender or size requirements for platelets, (although they do set male/female height/weight requirements for double red cell donation.)

I find it funny--for relatively similar cultures (OK, perhaps theoretically different in their means of providing healthcare) that one would allow females and one not. If we were comparing a country with a more conservative viewpoint of women (say, Sudan) and the UK or the US I wouldn't be so surprised. But this difference between the UK and the US surprises me.

Enlighten me please, science minded people.