Well, it's not shallow, actually, I don't think. One of the odd things you notice in Strike fanfic is how many writers want to make Robin very sexually confident. To be fair to the better ones, they do weave in the idea that Strike has given her that with his respectful behaviour towards her, but even if that were the case, it's waaaaay ahead of where we are now.
And I just don't buy it. We've not been told a lot about Robin's mind in this regard, but it really doesn't ring true to me. Whereas yes, Strike is apparently quite the good time. One of the reasons I think they would need to actually have a proper, relatively sober conversation before any shenanigans occur, rather than falling into bed drunk, is that there's quite a disparity in experience, and therefore maybe expectation.
In TB 58, it occurs to Robin first that there's a bed quite close, and the realization comes across as very nervy - tied in with her being afraid of 'giving herself away', and I get the sense that her reticence here is because she thinks Strike isn't interested because of low self esteem in that regard (cf all those mentions of Charlotte, and especially TB 60 where she clearly lays out that she's a poor comparison to the wonderful, exciting, beautiful Charlotte) and she doesn't want to make a fool of herself. I think she avoided that conversation moving towards sexy chat because she thought she would be rejected, and that's what would ruin the partnership.
Whereas Strike's thoughts about the bed, outlined better in TB 60, were about trying to remember when he changed the sheets, and therefore his fears about physical intimacy, are because he thinks getting involved and it ending badly is what will ruin the partnership.
That's quite a difference in starting mindset, and therefore sexual dynamic.