Yong Meng's article has rightly pointed out the downsides of exam-oriented learning (weak sight-reading, limited repertoire and loss of interest which was also mentioned by Theng Beng). But as Zensen said in the first comment, it ultimately boils down to the learner's objectives or purposes.

In defence of exams, these graded assessments are a tangible measure of one's progress, for the learner and for the parent. They are also a source of external motivation, which I believe, has its place alongside intrinsic motivation. Some kids may want to learn certain songs they like very much (e.g. from movies), but because they are unaware of the hard work and commitment needed to master the song, they may also give up eventually. Hence, being "forced" to learn something may not be as bad as it sounds.

The practical purposes would be, as Yong Meng mentioned, entry into MEP in schools or DSA, although an audition may also be held. Moreover, if a learner aspires to become a piano teacher, they would need to attain certification. A qualification from an established institution would enable employers to hire in a fair and objective way. If not, piano teachers would likely need to rely on personal connections or word-of-mouth recommendations.

I am currently try to 'influence' my eldest daughter who is 10years old to pickup piano. I think she got good height, fingers are Long enough and still flexible. She currently still prefer guitar over piano. I always believe piano is the fundamental basic of all musical instruments. Once you knew piano then you could pick up and learn other musical instruments.