Likely because we still have no widely known mobile wallet ( monerujo could need some marketing ), no HW and people likely just hold their Moneroj on exchanges
The GUI is pretty functional, I don't think serious holders (hodlers?) are all on exchange at all.
An HW will come - it's a matter of time only, it's simply that Monero is more sophisticated than other Bitcoin 'clones' and therefore not as simple to copy/paste code into a standard HW.
Monero is superior tech, they need to catch up, not us.