Documentation Before Offer Letter?

So I assume that you all have gone through the same but wanted to check your feelings. Why is it that we have to share all the documentation before even they make an offer? I do understand that they need some documentation for verification purpose but lot of times they are going to ask for current offer letter \ any in-hand offers even before the interview itself. Can we all agree to no share such letters before the getting the offer \ confirmation? That is at least they should communicate to you that you have cleared all the rounds and now the documentation verification is pending and is the final step before offer generation.

PS: Sharing the in-hand offer reduces your chance of getting a higher package because most of the the companies have a % range when jumping and is one the reason why they ask for the same. Personally I won't even share the current package but some of the companies would not accommodate you if you are not willing to share your current offer. But I have taken a position on not sharing the offer letters after making the mistake myself.