he feels guilty about Pietro's death. feels like it's partly his fault. he should have died instead. and he probably thinks Wanda hates him for that, so he tries to show her how much he's indebted to her brother and how much he loves her and she understands and accepts him as her honorary adopted father.
Clint Barton aka Not Just a Dude With a Bow.
The thing is, he'd do this. Clint Barton would hide in your ducts and say no when asked about it while still in said ducts