Picture this: you sign up for a race (say, a half marathon), fork over the entry fee (£40), select your age, gender (F), expected finishing time and t-shirt size (XS).
On race day you finish strong, sailing through the finish with your new PB. You pick up your race medal, banana, water bottle and your finisher's t-shirt.
You hold the t-shirt up. It seems a little... large. Your runner's high dissipates as with a sinking heart you realise this is a "unisex" t-shirt.
"Unisex" t-shirts are presumably called that because they only fit one sex, namely men. This despite the fact that around half of the participants in the race you just completed were women. You sigh. At least you can wear it to bed.
When you get home you stuff your £40, technical pyjama top in a drawer and forget about it because you also own actual pyjamas that are much nicer. Every weekend after the race you see at least one man out wearing his race t-shirt. You assume the women all shoved theirs in the pyjama drawer too.
Anyway, £40 is a ridiculous price for a t-shirt*
* I may have gone and bought a £45 fitted t-shirt the very next day