How do you know they didntnt all use felix? And it could go terribly wrong, plus you're not to use it so much

In the ron quiddutch scene, they didnt use it. Only when he asked for slughorns memory

Plus felix felicis might be just water and everyone tricking him loll

It's probably incredibly rate, and there's better things than relying on felix, which is why all those withches/wizards ate so great- Harry just had it, then it helped

Lol snape had loads of veritaserum and slughorn just had it. Its takes bout 6 months to make felix felicis but slughorn was made teacher 2 months before, and its such a coincedence

For Veritaserum:

(From the wiki) For the same reasons muggles do not use polygraph tests in court, Veritaserum is no more reliable than its Muggle counterpart. Since some wizards and witches can resist its effects while others cannot, Veritaserum is "unfair and unreliable to use at a trial" and would be difficult to use as definite proof of guilt or innocence.

For Felix Felicis:

(From the wiki) Luck can only get you so far, Harry... Luck is not powerful enough to get through a powerful incantation.

There is more to it than just this. Take a look at the limitations section on wiki pages.

I see.

Ok...