No one is saying non-mums cant be tired, anyone can be tired. The difference is if a non-mum is tired they can rest(sleep), things can be dropped, parties can be not gone to, sick days can be taken. But when you have a small (emphasis on small, this tiredness really only applies when they are young) person who needs you the rest is not possible. The thing about motherhood though.... its only temporary, the kids grow, start to sleep through the night, go to school etc.