Yeah, because giving it 200+ penetration is really going to affect balance when the best armoured vehicle around at the eighth minute mark is a Stuart. It already penetrates everything at the eighth minute mark.
Its going to affect every single armored unit with more then 160 armor for allies.
It'll make KV tanks even more irrelevant, it'll completely remove the only purpose of churchill MK VII, it'll dominish EZ-8 survivability.
It would also completely remove the need to tech above med truck vs heavy tanks.
All of that for no particular reason except "historical balance" jerking.
The Jagdpanzer IV can already reliably penetrate mediums, so - again - this change would only affect its performance against heavies.
Which creates cost effectiveness imbaalnce vs heaveis, resulting in great overperformance against them and the mandatory adjustment with either, reduction of fire rate to 7-9 seconds(to equalize its DPS with firefly who would still have much less pen) or to greatly increase its cost.
Also, @ people saying the Jagdpanzer is the best TD in the game. It is. But it had better be when it costs as much as two StuGs, which have a much greater damage output and are better against infantry.
It costs 15 fuel more then SU-85.
Its balanced as 135 fuel vehicle.
It performs as 135 fuel TD.
Again, don't try to fix what isn't broken.