The salary floor means you have to pay at least $35000, even if you had no players for example. If you have players with salaries of more than $35000, you're already paying at least $35000 so the salary floor is irrelevant to you.
Like people are saying, this was to prevent tanking. Suppose you were in the NBBA for example, you have really high attendance revenue and TV contract. Suppose you wanted to tank and there was no salary floor, so you sold all of your players and bought 3 $2k scrubs. You would make a huge profit, but since you would be completely uncompetitive it wouldn't be fair and would ruin the game for other players. So the salary floor provides an incentive for you to at least keep enough players to be competitive.