... this is all about control and reducing the RISK of a negative reaction towards the referee
For me - if a player wants to go quick - let them - they know the risk if they muck it up ... once we are in ceremonial mode, yep, I'm looking at the GK, HOPING he/she is getting themselves ready, maybe taking a few extra seconds lining up the wall (giving them the preventive chat about hand / arm movement, etc.) - all the time hoping the GK is in a position that I think indicates readiness (i.e. not leaning on a post flapping a hand from side to side!) ... then blow the loudest whistle I can ... I'm not going to check if the individual player (GK) is ready as I'm not going to check every other player is ready
(yes - I will wave to the GK at the start of each half - so happy to be called out on this one)
Slightly different - but - I know a ref who will shout "face forward" on every re-start - including throw-ins - may just be a habit - but it definitely helps reduce the possibility of someone saying they weren't ready