In addition to the better than decent chance that the number 9 pick in this draft is just as good as the number 1 pick, I think that not tanking is good for maintaining a franchise standard and winning culture, good for keeping their fanbase engaged, and just generally overall good karma in the eyes of the basketball gods.
I don't begrudge the Spurs front office for not fully tanking after trading Kawhi even though it may have been the smart thing to do at the time. In many ways, I admire it. I like to think in my warped little mind that things worked out the way they did with Wemby for the same reasons. Watch Memphis defy the lottery odds and end up in the top 3 anyway.