The reason cited even in privately held companies is pretty much because everyone else is doing it.

Their COGS (Cost of Goods Sold) rises every year. The markup on licenses, the physical hardware, the shrinkflation from the manufacturer, and COLA (Cost of Living Adjustments) for staff all cut into the operating expenses (or profit) of the company.

Under capitalism there are hardly any checks to this, so even companies that are not seeking to grow must raise rates else they will take a loss every year.