Because it is an absolutely terrible system to “fix” the ability to spawn with more vehicles than normally would be the limit if you click spawn at the same time.
Similar to the “fix” for the bug where if you drop and pick up a weapon repeatedly, it can change into another gun. Their fix? If you drop a weapon, it now vanishes into the void.
Gaijin is known for making these bandaid fixes that make things worse, just look at how they “fixed” abusable map positions by making all somewhat steep slopes made of soap. And it seems like Darkflow is copying them.
Yes, moving back the spawn would probably be the best. The ones we have rn are a bit too close for comfortable attack runs anyways.