I comprehend what you are saying Laura on one hand. I also do not honestly believe in '"wings'", "Rainbow Bridge" or the likes. When a dog dies, a dog dies. End of story for me. But that's just me. Others believe different things, and we are all entitled to our different beliefs.
But on the other hand, I think many ppl use those terms as they feel it is kinder and gentler. Like many ppl wouldn't say "I"m so sorry so-and-so died. They tend to state "I'm so sorry so-and-so passed away."
I think it comes down to 'each to their own' and how each person feels comfortable expressing their thoughts and beliefs.