Positively framed the functionality has grown much faster than battery capacity has evolved. Phones back in the day were phones, now they're pocket computers. Ignoring the industry claims I feel like batteries have improved, comparing for example Laptops from 10 or 15 years ago with modern ones.
Another thing that people might not even be consciously aware of is that they're using their mobile devices more these days than in the past, which obviously leads to faster drained batteries.