I too stand in awe of these players who can make 1000 moves a day and still put together a vaguely cogent game of chess. Of course they play much weaker than their OTB strength but in this modern computer age they may well have come to the conclusion that playing their best game only brings them up against well researched openings and engine assisted players time after time facing opponents they can never beat. Blitz simul play is it's own discipline and I'm sure you can get better at it with practice. With some here it is evident they have a slimmed down opening repertoire which they either know well or is readily accessible when they play so that consultation does not "waste" valuable time. If a line goes wrong then they will play an alternative next game. I don't know if texasnurse does that but the notes to the game quoted by Paul Leggett indicate she pays attention to some of what goes on! When the next board pops up you have to be able to immediately recognize if it is one of your regular opening positions and if so which opening it is. For example I have blundered a piece by confusing the black side of a Guioco Piano with a Cordel Ruy Lopez or Kings Gambit declined simply because the bishop was on c5 and I assumed I knew what I was doing. Then you have to remember the relevant set ups you are trying to push for whilst avoiding as far as possible complex tactical lines that are hard to calculate at speed. In his best games book Alekhine said that he had taken over half an hour to work out the ramifications of a sacrificial sequence ten or more moves deep so the rest of us mortals have no chance. With Blitz simuls on this site it may be a day or two or a week or more before you see the position again and, unless you leave yourself a note, you may not remember your winning line and so the game will often lack the sense of continuity and is further fertile ground for errors. Another factor is that if you play stronger players on correspondence sites they never seem to move, whereas the weaker ones always do, unless they are playing a high game load themselves. One way to even the score is to play a lot of them at once and you can get a little of that OTB Buzz.
I've played texasnurse a number of times and I reckon she gives most of her moves 10-15 seconds. At 10 seconds a move a 1000 moves requires 2 hour 46 minutes per day whereas 15 seconds a move requires 4 hours 6 minutes. If you are then able to swap modes and go and win your state championship without dropping into blitz mode and making blunders then all the more kudos.
Anyway, I think chess can mean different things to the same people at different times in their lives. Sometimes it's serious, it's about status within teams and clubs, sometimes it's simply an amusement, a distraction keeping an aging mind from existential worries or maybe it's about finding a way to get those nice chemicals coursing through one's veins by taking on more than you can handle and handling it all the same. There do not have to be imperatives.