Why do pets have to get old?

Got sad news that Heidi is pretty much blind.  She is only 7 years old.  We thought her eyes looked a bit cloudy, and one eye appeared more cloudy than the other, but had no idea how bad it was until we went for her annual check up last week.  Basically, the only reason she gets around is through her sense of smell and familiarity.  She knows the house, so she doesn't bump into things, though she still does it occasionally.  We have referrals to a couple Vet Eye Docs to get her checked out and see how much it would be to give her the surgery.  I hear it can be up to $3000 - OY - which, of course we will find some way to pay if that is the case.  We have pet insurance but in most cases this surgery is not covered because they will determine it was "hereditary or congenital" - they always have ways to get out of paying.  But we need to get it done before our move when nothing will be familiar to her.  If you know us, you know how much we love our dog...she was our first kid and she is part of the family, so not giving her the care that she needs would be like not giving Scotty, Zac or Trev something they needed.  It is sad to see her get older and we are really not ready for it.