Future's market is made for champions that need to get to item thresholds sooner.
Viktor with his first upgrade.
Ryze with RoA and Tear. Since they are both time based items. The sooner you get them the better.
Normal champions that aren't time gated or have a stupidly high first item buy (viktor's first upgrade) wouldn't need it or want it.
But imagine getting a whole item one minute, sometimes up to three minutes sooner. Now you can argue, why three minutes?
Because back timings, minion waves, etc. You can't just leave lane because you want to anymore. You lose your tower way too fast. A bad back timing could result in the enemy jungler/ other laner shoving and taking your tower.
So futures market is super nice, with biscuits. It made it even nicer. Since biscuits nullified a lot of that pressure of mana/getting poked out early.
Now its going to be perfect timing and biscuits. 0 reason to take futures market over biscuits since the pay off has no drawbacks vs futures market does.
The only way that this change makes sense is if they address EVERY single issue in patch 8.4