Because it started from Monero, back then there were no good Monero wallets and to use it, it was all hacky and from the CLI, only the real techies used monero that time

but now there are more devs and the focus can be wider so there is a bitcoin-only wallet coming, more bitcoin privacy features will come, and cupcake can also be used for bitcoin signing, or silent payments spending, while another hot phone wallet is view-only, or silent payments scan-only, etc