Tony has always defended himself through evasive
manoeuvres, and never used shields.
Yet in Infinity War, he is using shields left and right. (The only time he shielded himself was in Iron Man 1, when he opened flaps in his gauntlet, and that was because he down low on power and couldn’t fly away.)
Tony realised that the team has lost a “shield”, so he took it upon himself to become one. He built a shield that could withstand the power of an Infinity Stone. Because he always knew the fight was coming, a bigger threat is on the horizon and he needed to be ready.
Meanwhile, Tony designed new shield for Cap (despite all the Civil War mess), new “magic” belt for Thor (despite not knowing whether Thor will return), ensured Hulkbuster was accessible to Bruce (despite Bruce being MIA) and built space-travel-safe spider-themed nano-suits for Peter (despite Peter not being an avenger yet).
tony as a stay at home dad trophy husband is such a good tier like imagine pepper comes back from a business trip on dubai to tony cooking italian with harley while peter helps morgan with her math homework, tells him she just signed another multimillionaire contract because she knows tony’s going to spend that money on clothes and lingerie, and possibly another trip to disneyland with the kids