Why does the luch need veterancy to less get vision than a M3A3 at vet 0?
Default Sight = 35 Range
Sight Options Available to USF:
M20 = 50 Range
Stuart = 45 Range @Vet 1
Pathfinder = 50 Range
Major = 50 Range @Vet1 Also has Call in Scout Plane
Sight Options Available to OKW:
Kubelwagon = 50 Range + Minimap MapHack Ability
Volgrenadiers = 45 Range @Vet4
Jaeger Light Infantry = 50
Sturm Officer = 50
Panzerfüsilier = 35 but has Flares
SdKfz 221 Scout Car = 50 Range
Panzer II "Luchs" Light Tank = 35 Range, 45 Range @Vet3
Puma = 50 Range
Panzer IV = 35 Range, 42 Range @Vet 5, +10 Sight Range with Panzer Commander Upgrade
Panther = 35 Range, 42 Range @Vet 5, +10 Sight Range With Panzer Commander Upgrade
Flammpanzer 38 Hetzer = 50 Range @Vet 5
Sturmtiger = 45 Range @Vet 4
Command Panther = 50 Range, Aura provides +15 Vision Range to all Vehicles
King Tiger = 35 Range Default, 50 Range @Vet 1 with Spearhead Ability, +10 Sight Range with Panzer Commander Upgrade and stacks with Spearhead for a Total of +60 Vision
So to answer your question Vipper, it is because Luch's does not need the extra vision and it is only there to make use of the Vet 4 bonus which gives +5 Attack Range. Having a vehicle with 40 Attack Range and only 35 Vision would make the Vet 4 bonus useless.