I did maths, further maths and physics A levels. Along with languages.
I have encouraged and promoted maths and science with all my dc. Dd2 (now 8) as much as the others.
Didn't stop her becoming completely discouraged when she got to school, and her peers were all' oh, maths isn't for girls' and 'you mist be a boy, you have short hair and don't like pink' She was not strong enough, confidence wise, to carry it off, and so the only option was for her to fit in.
The rest of the world counts. And wider society pushes girls towards pink, domestic tasks (through things like play) and away from science and engineering.
Dd2 completely changed what she liked and disliked, aged 3'to fit in with her peers. Because that's what she needed to do. And what she was socialised to do by her preschool workers (eg steered towards quiet, indoor play so as to not get her dress dirty, when dd2 wanted to play on the pirate ship outside, not helped by the fact that the boys were playing out, and girls were mostly playing with dolls and so dd2 learned pretty swiftly to play with the dolls, like pink, etc. She hates standing out.)
I have no problem with her liking pink, if she actually likes it (rather than liking it to,fit in, but then I can't change her personality type). I have no problem with a wide range of playthings, accessible to both boys and girls.
I have huge problems with the way toys are marketed - once dd2 was indoctrinated by her peers, she began to naturally swerve towards the pink aisles in toy shops, whereas before she would seek out what she wanted. And the pink aisles are full of very different toys than the rest of the shop, as described on this thread. I know lego friends have finally brought out some non-stereotyped girls sets, but it's been a long time coming, and isn't good enough.
This stuff does matter. It does have an impact. I am delighted that your dds are so confident and self assured that they can always make their own choices completely untouched by peers or marketing ploys. Mine, despite my best efforts, isn't, and is (entirely naturally) keen to fit in with her peers and societal expectations. And those societal expectations are generally a bit shit if you're a girl.
And then, to top,it all off, the one range of toys which everyone knows, from their own childhood was a great leveller - no gender divide, just bricks to pile in and play with - brings,out a highly stereyped range, aimed solely at girls. And then a second range, also aimed at girls, with similar connotations of magic, whimsy and domestic bliss (the Elves range). Just why? Another shop where there is now a pink aisle for dd2 to gravitate towards, while I have to, yet again, try to redress the balance. It's just so unnecessary.