I could be wrong here but one advantage regarding retirement and betting each match one by one instead of a future bet...if djoker retires for some reason does your future bet lose? Idk bookmakers rules but the 2 books I use, nitrogen and heritage, nitro voids all bets if there's a retirement and heritage voids some bets depending if the 1st set was completed.
My point is if you bet djoker each round and he retires in let's say the 3rd round, you may get a push where your future bet is in the toilet.
I'm not 100 this is accurate line of thinking tho because I don't bet tennis futures very much.