Hogwarts classes and textbooks

[Jerri/Dan Chase]

No: HPFGUIDX 182625

All the discussions of Harry's academic abilities (or lack thereof) 
and how the students who attended Hogwarts learned the basics like 
reading and maths (which I recall JKR said that some went to muggle 
elementary type schools and others were home schooled), has reminded 
me of a question in my mind about one of the classes that Harry and 
apparently all Hogwart's students took every year for the first 5 
years of school.  And that is Astronomy.

And my question is:

Why do they take Astronomy, for FIVE years, when there is so much 
other stuff that they don't have time to study?

I don't recall every seeing anyone USE astronomy.  In divination there 
is some mention of plant and star movements, and they having learned 
things in astronomy.  But not everyone takes divination, and the 
astronomy related parts of divination are small, except perhaps when 
taught by a certain replacement teacher!

So, can anyone else find anyplace in the books where astronomy is 
used?

That is, any reason for this class except to provide an astronomy 
tower, from which Norbert can depart, HRH and friends can see Hagrid's 
confrontation with Umbridge's staff, followed by McGonagall's 
response, and finally for Dumbledore to fall off?

And, why is Fantastic Beasts and Where to Find Them a required text 
for first year students at Hogwarts, when they don't take Care of 
Magical Creatures classes until third year?  And isn't it supposed to 
be an optional class, even then?  Every other book on their list is 
directly related to a class.

And if the Weasley family is hard up for money, do they really need a 
complete set of Lockhart books for each of their five children at 
Hogwarts that year?  Can't they share at all?

(By the way, I do own a copy of FB&WTFT and enjoy it a lot, but I do 
wonder.)

Jerri