それに、体操服もいまだにブルマーなんだよね。なんでだろ？

、。？

And on top of that, the gym clothes still include bloomers. Why is that, I wonder?

Literal

Moreover, gym-clothes [also-も] still bloomers [copula-なんだよね]. Why [wonder-だろ]?

体操服 'gym clothes.' ブルマー 'bloomers' — the short athletic bloomers once standard in Japanese school PE uniforms, now largely replaced due to criticism. いまだに 'still, even now' emphasizes that a change was expected but hasn't happened. なんでだろ？ is a casual wondering question.