Sure, I will try to:
Player A is not part of a big group (mistake #1 you could say).
By the last patch CCP deployed, the available of ice belts shrunk to roughly 30% (more info in Ice Mining). The rocks didn’t become smaller, but the ice belts just don’t spawn. In some systems not for weeks (no joke or exaggeration).
Player A decides to give it a try with an Endurance. It’s fast and small and has a good mining amount per ice ore unit. The next ice belt is 8-10 jumps away. Player A has no structures there or nearby so A is forced to haul everything uncompressed.
Now comes the issue: an Endurance has only cargo for 15 units. Even with a small fleet consisting of Porpoise and many Endurances or Barges, that won’t scale for Ice Ore.
Ice Ore is big. 100,000 m³ of Ice ore has a completely different meaning than 100,000 m³ of any other ore.
Direct answer: it’s not necessary by mechanics as you could hauler everything. At the end the current, active ice belt respawn mechanics only helps the big groups. With the Neptune, smaller groups could steal the Ice.
If CCP decides to revert to the old spawn mechanics (don’t believe in that) the Neptune would be useless.