Also going straight up is a much higher risk operation than having some forward speed. The timeframe to eject in case of a problem is very very short when you'r

Also going straight up is a much higher risk operation than having some forward speed. The timeframe to eject in case of a problem is very very short when you're "hovering" while with forward speed the jet has much more stability buying you time. Helicopters also tend to take off with forward speed if conditions permit. Not because of ejection options (they don't have them), but because of energy available and options in case of an engine failure. Forward speed is "energy in the bank" which you can use if (one of) your engine(s) quits.