"Being happy that a game you like is getting good sales and thus a chance for a sequel" is like 2% of all sales-related posts. The other 98% is either defending bad games because they sell well, or shitting on games they don't like for not selling well. It lends an air of legitimacy and even maturity to people's position over what is essentially personal opinions on videogames, without needing to actually argue for their qualities or lack thereof; it's a cop-out and the lowest hanging fruit in the tree. There are very, very few times where using sales to settle an argument is not disingenuous; most people using sales in an argument are doing it entirely for the same old "sales -> popularity -> quality" fallacious correlation, and when this fallacy is pointed out, they accuse whoever did it of being culturally elitist.
(there is also less correlation between sales and viability than people posit. For one, they almost never correct for games' budgets until they are pointed out to them, conveniently forgetting indie and lower budget games become profitable much more easily than AAA games.)
