Bass Fretboard

I don't know for sure but it seems to me that the fretboard on a fretless bass needs to be made from very hard wood to help sustain but also to keep it from wearing quickly. My Yamaha fretless has a lot more wear on the fretboard than my Carvin fretted bass even though the Carvin probably has had hundreds of times more playing use. Is this because the Yamaha board is softer than the ebony on the Carvin? Probably but also not having frets has to contribute to some of the wear.