40k is weird. The scales are often entirely off. Considering the stated populations and areas involved. Or the amount of equipment fielded.

This comes from it fundamentally being small scale skirmish game. So realistic army sizes are not possible. And on other hand you need some level of game balance. You can't expect one side to have dozen models and other to field thousands or tens of thousands.

And even there. Considering stated population of any reasonably build world to be in billions and more populated to go to hundreds of billions. Number of normal humans you could stick a weapon in hands and told to shoot at that direction would still be in at least millions if not billions. A few thousand whatever can do very little against that.