I think it's become a giant game of chicken, really. "The People" know that the restrictions can't last forever. At some point the SG is going to have to release them. Furlough will end, the rest of the uk will reopen and people will holiday and do business there and Scottish businesses will lose out.
While this happens, yes, cases may increase, but hospitalisations and deaths (theoretically) won't - regardless of how much Scotland is open. At some point the SG will have to capitulate to accept living with the virus circulating, but not being so disruptive and dangerous.
People disobeying the "rules" at the moment I think have realised that nothing they do or don't do will affect how quickly that happens - so they've just decided to do as much as they can and minimise the misery to them! Even if their actions increase cases, it won't lead to substantial numbers of deaths once the vulnerable are vaccinated, and it won't affect how quickly we move out of lockdown, as that will largely be driven by the UK government, which has the power to extend furlough, open eg hospitality and retail for the larger part of the UKs population and so on. Scotland could of course open before England, theoretically, if cases were significantly better, but I think the SGs past actions suggest this is unlikely, so not worth aiming for!
I'm not saying it's right, but I can understand the thinking.