[arch-general] Why irrelevant updates?

[Francis Gerund]

Sometimes pacman presents updates that just don't seem to apply to my
system.

Just one example: sudo pacman -Syyuv presents btrfs-progs, even though:

1)  I do not, and have not, used the Btrfs file system with my Arch setup.

2)  It is "Required by: None"

3)  It is "Optional for: None"

But I hate to reject it. After all, there must be some reason it was
presented . . .  right?

So, if I just say "yes" to all upgrades, won't my system over time get
weighed down by excess stuff, until it grinds to a halt?

Or, if I just make my best guess at what is really need and reject the
rest, won't I have a Frankenstein system that will eventually break?

And why, why, why doesn't it just present upgrades appropriate for my
system?