aside from drawing, a pen can be preferable to a mouse for those who find constant mouse tiring/uncomfortable

you are right paul xara is not artistic in that sense, it is slow and steady, the freehand pen has 'wobble' where the program is guestimating where you want to go next, useful maybe in certain cases but not for fast expressive drawing where the brush engine gives up trying to follow your stroke because it cannot keep up, the wobble is instrumental in this as it all needs to be processed in real time

that said you can be very artistic in the traditional vector way