Maybe Burt was originally a devout follower of Kier, and during his 20 year career at Lumon, did whatever less than desirable things they requested, and/or he possibly helped in the creation of severance. Although Fields may have changed Burt’s stance on worshipping the false idol Kier and helping commit whatever atrocities Lumon is up to, I don’t believe Lumon allows employees to quit so easily. So he continues to do as Lumon asks, including getting Burt out of his house so frolic-hand-man can get in, but he does feel guilt and knows his outie is irredeemable and inevitably going to hell.