This is sort of fascinating to me as someone who does wear makeup for the special occasions and has then had to sit through her husband informing her that he prefers her without it. (He also prefers my hair undyed, which is unfortunate for him as I prefer not to wear my genetic hair color in favor of something that suits my self image better.) I like the comment suggestions of asking her if she would help him learn to do it for himself, or if she would consider being a model for him to learn on, which would give an opening for her to say so if the cost or skin sensitivity was a factor. Or anything else.

For what it's worth, I'm not reading this letter as "treating women as a monolith" or being unaware of the societal expectations around it; the fact that he's worrying whether he can ask at all suggests he's trying to work it out in his own head, on his own, without putting that processing on her, and I appreciate that. But I think my read is in teh minority here.