Opimizes only PC version

Hi! I have adaptive site, no special version for mobile user. I test score of pages via PageSpeed Insights and I see strange results.
If I enable caching there is some effect only for PC: from 92-94 to 99 in PageSpeed Insights
But caching has absolutely no effect on Mobile: 52-54 with desabled cache and 52-54 with enabled cache.
How to explain this?