Yeah, most systems came with cartridge ports, so I guess that's why cartridges are more common. The data drives were optional. My Coleco Adam computer had both standard, so I had some games on tape.
The thing is that even the most common type of cartridge usually is worth at least $4 (I know some buy them in surplus for less) while most tapes have a value around $1-2 so selling and wrapping those individually usually isn't worth it.