Because the deposition, when played for a jury in a civil suit, may cause them to find against you or the party you align with.
"...party you align with." That is a big assumption. I prefer not to align. If for whatever reason I am aligning with party I will of course take that into account.
Because mostly the answers don't matter and the only thing that does matter is the fact finder's opinion of the parties.
So your are telling me that we only have kangaroo courts? Well I sort of suspected it. thanks for confirming.