Apparition; a need or just speciality

[buzzy_adam91]

Hello there. I hope you all are fine..

I just wanna ask to everybody about the apparition lessons in the 6th
book. In the book state that
'IF YOU ARE SEVENTEEN YEARS OF AGE, OR WILL TURN SEVENTEEN ON OR
BEFORE 31ST AUGUST,YOU ARE ELIGIBLE FOR A TWELVE-WEEK COURSE OF
APPARATION LESSONSFROM A MINISTRY OF MAGIC APPARATION INTRUCTOR.
PLEASE SIGN BELOW IF YOU WOULD LIKE TO PARTICIPATE. COST: 12GALLEONS.
Harry and Ron joined the crowd that was jostling around the notice
taking it in turns to write their names......'
 It seems that everybody interested on it. But in the 5th book, all
visitors to the Quidditch World Cup arriving there by Portkey
transportation.. em, I found scatterbrains when I try to think about
this. Plus Amos Diggory prefer Portkey more than Apparition.. and
Harry also state that,
'..maybe it's better when you do it yourself, I didn't really enjoy
it much when Dumbledore took me along for the ride...'
Plus the Weasleys choose to go to the Diagon Alley by the Floo-Network.

I hope someone will give me the answer..
Thanks for now.

buzzy_adam91