Spank your child and create a criminal

[Philippus Flavius Homovallumus]

But a lot of that was earlier on, during the apogee of the empire. And it may have helped the empire given that they could select worthy heirs rather than deal with entitled brats.

That's beside the point - Roman Emperors repeatedly FAILED to produce sons so they HAD to adopt.

Basically, their little legionaries weren't as effective as the full size ones.