Practising , in the beginner stages, can be quite onerous. Especially if one only has specific learning tasks - scales, part of a tune, etc. Given other things to do - make up a tune, 20 seconds long, just using D,E, F#,and B -for example, or play CABBAGE in as many different ways you can all over the piano. There are hundreds of ideas, will hopefully mean playing does NOT just mean learning tunes by rote, till they're perfect, then, so what ?
To me, practising can be like eating - we certainly do it 2 or 3 times a day, every day, and we certainly don't save it all up till the end of the week, just before the next lesson !!Short sessions often work well, as the 'boredom factor' doesn't have time to set in.Particularly in the early stages, when knowledge is limited, so only a few things can be 'learnt'.
There cannot possibly be a definitive answer to this question, as every child/beginner is different. Some will love performing a newly learnt piece, others hate it.Incentives to practise, let alone to learn, will vary from one individual to another.As a child, mine were 'no treats till you've done it'. It worked, but at the time my parents were hated for it. 50 yrs on, I'd be cursing them if they hadn't done it, 'cos nothing else worked - I play every day, and love it !!