j'nuh - That, personally, is not what I'd call rotation. That is what I'd call "flog the first choice as much as possible" with a couple of rests and missed games for internationals. Nor would I call 3 starts (potentially 4) a decent platform for a player to make his case.
Not being funny, but Laidlaw isn't much short of a 1000 minutes for club and country so far this season. With 15 games left for him to be selected in as a more or less minimum, assuming he isn't played in 6N rest weeks/Glaws don't win their CC quarter-final, he's going to be around 2,000 total (if fit). If there was a summer tour he'd probably hit 2,200 or so. A player hitting that total every season is a player who, in the long run, is a player who will probably either lose form, lose fitness, or both. You can't keep playing Laidlaw this much. If he's genuinely that important to Glaws, then he needs to be protected, and that means rotation.
Which would have allowed Robson a platform to recapture his form and make a case for international honours - enough gametime to persuade him its worth staying - and in future, provide a international standard scrum-half who has a long standing natural understanding with his team mates. Yes, Glaws have enough money to do ok if they need to attract another scrum-half down the line, but no amount of money can reproduce what they could get from Robson. Everyone knows he has the ability.
Sorry, but I don't see any good reason for this.