Manufacturers for most devices are going cheap out on everything they can, see: cell phone industry and 3.5mm jacks, microSD card slots, etc. More storage ups the cost by quite a bit more than the storage itself actually costs for a new phone (but don’t worry, the phone manufacturer offers cloud storage (as a paid service)!
Storage has improved amazingly over a short period of time, there’s individual drives with more than 20 terabytes these days