For the same reason they have to wake you up to take a sleeping pill. . . "That's how we do it here."
Honestly, I became so tired of finger-sticks for INR testing that I finally told them "If you don't stop that right now, I'm going to go out in the hallway and cry as loud as I can. Nobody wants to see an old man out in the hallway crying. Won't look good on you." They became a bit more considerate after that.
A couple of things that mattered to me:
1. Glasses or reading glasses, if you need them. Maybe even spares.
2. Cell phone, tablet AND CHARGERS. Maybe also an extension cord.
Things that didn't really matter to me:
1. mp3 or music player and earphones. I just didn't care to listen.
2. Books or e-reader. Same reason. Also, I really couldn't concentrate.
3. Favorite snack foods. I had little appetite, and almost everything tasted the same -- like industrial chemicals. It took weeks after surgery before my sense of taste returned to normal. Until then, if we fumbled upon something that tasted "good" to me, my wife stocked up. I ate tons of vanilla wafers and drank lots of ginger ale for the first few weeks.