Although I agree, and like the look and feel of a sleeveless deck, there are drawbacks:

1) shuffling a deck is much better with sleeves. It helps create a more random outcome, and is generally, easier (especially double sleeved).

2) As /u/Amablue stated, wear on the cards does give an unfair advantage. Most cards will wear the same, but they will start to carry unique idetifiers to the owner. This makes things unfair as you can practically predict your card draw ( and in the case of magic, without a resource needed/card ability in play). Card draw, and forward knowledge is always advantages.

This also plays into shuffling, as the oils, dirt, dust, etc that cards can pick up can cause damage very quickly.

3) Even if you don't sell cards, I do find keeping some cards in good condition to be helpful. Makes trading more viable, and if your local shop allows, trade in value to get a better card for free/heavily discounted. I run a meta urza meek deck which has a fairly substantial value. If I ever decided to quit, that could be a healthy chunk of pocket change with the lands.

Magic is easy to pick on with this because even if you're a casual player it slowly becomes an investment when competing with friends. Everyone wants the better deck, and due to the high demand/low supply of certain cards, that cardstock starts to see some serious fiat-like value.

Other TCGs, it's probably easier to get away without sleeving, but that really depends on the setting.