Obviously they don’t need them. But the prevalence of wheelchairs is because of out modern world and architecture. I did research on the history of wherlchairs. The first self propelled chair was invented in 1655 in Germany. Before this point you had to be carted around. No afventurer is going to be carted around, wheelchairs simply did not exist during the typical dnd time period. Besides, the early wheelchairs were only for the wealthy, those who did not have to labor and could pursue other interests. Paved roads as we know them came into existence in the 18th century, and around this time hospitals began using them to cart patients around. Then wheelchairs became more widespread.

https://www.britannica.com/technology/history-of-the-wheelchair