Sales follow the tradition of supply and demand. Products come out at their highest price because of expectations and hype. Then, as interest wanes, the publisher continues to make some sales by reducing price to tempt the less interested parties.
But this isn't the formula for all games. While we might agree that games from 2000 or even 2010 are "showing their age", at this point 5 to 8-year-old games are less and less likely to be seen as 'too old' by comparison to hot releases. Some publishers have picked up on that theme, and doubled down on the commitment to the idea that their games have high longevity and appeal; making the most of their capitalistic venture for better or worse.
I recently was reminded of an indie game I had put on my wishlist several years back, but never ended up buying because it simply had never gone on sale - but looking at it now, not only did it maintain extremely positive user reviews, I also saw that its lowest all-time price was barely a few dollars off of its original price.
In the AAA space, the easiest place to see this happening is with Nintendo. Anyone hoping to buy an old Legend of Zelda game for cheap will often be disappointed - the company is so insistent on its quality, they pretty much never give price reductions. And, with some occasional exceptions, their claims tend to be proven right.
In the indie space, the most prominent example of this practice is Factorio, a popular factory-building game that has continued receiving updates, and has even had its base price increased from its original (complete with a warning announcement, encouraging people to purchase at its lower price while it's still available).
Developers deserve to make a buck, and personally I can't say I've ever seen this practice negatively. Continuing to charge $25 for a good game, years after it came out, speaks to confidence in a product (even if most of us are annoyed at AAA games now costing $70). I sort of came to this realization from doing some accounting to find that I'd likely spent over $100 a year on game "bundles" that usually contain trashy games I'm liable to spend less than a few hours in.
For those without any discussion comments, what games on Steam or elsewhere have you enjoyed that you've never seen get the free advertising of a "40% off sale"?
I’ve heard that for smaller studios it is incredibly important to get those early sales. Their margins are often very small (if they exist at all) so getting early and continued support is often vital.
Indie games are pretty much the only ones I still buy on release.