I was thinking another reason... Old bundles with full themed collections of games in the same series, or all titles from same company bundled together (like Square Enix for example), are now gone.

This.

Anyway, it's obviously done this way to get people to spend more, in the hope you buy something now, and then if something you want more appears later, you'll grind your teeth but buy it too.

Yes, but all the days that I refrain from buying anything from GOG, I could easily spend the money on...anything else, including games from another source...
Anyway, as you said.
As I said to Faitful, by avoiding buying from here and wait till the last day, there is a higher chance you will spend your money elsewhere and not on GOG.
Perhaps that's just me.

Sure, that's the rational approach, but people are seldom so rational and most stores tend to encourage and thrive on people's irrational and impulsive spending habits.

that doesn't make it okay and it just perpetuates issues with society (consumerism, greed, competition, etc.)

I wish more companies would set good examples with good practices and ethics, but then greed is what drives business so that's hard to make happen.

I got it! Reverse the process. Everything that's going to be on sale is available for, say, the first three days, and then slowly and randomly remove some games from the sale. We still get to see at the beginning the full list of discounted games, and the other folks get the excitement of seeing what changes from day to day.

XD

In all seriousness, for those on tighter budgets the later additions might get passed by. Or even not on a tight budget, later titles might be passed over since, "Eh, I already spent $28 here at Christmas time..." Maybe not the best type of sale for Christmas, where there are a lot of other things competing for discretionary funds and the customers' attention.

The sales periods are known in advance, it's better to plan ahead and save money just for the occasion and try to strictly stick to your budget and the highest priorities on your wishlist.

It's because they want you to spend as much money as possible. Capitalism at work. Anyway, patience is a virtue so just wait until the end of the sales.

Must I buy the game now or can I wait 'til I get home? Just imagine the thrill! And if nothing else, I'm sure it would make people quite active on the forum for the duration of the sale. ;-)

That's why I just check my wishlist and see what's discounted.

It's very easy to remedy this problem too. The promo page already has subtitles like "Notable", "Today's Highlights" "Today's recommended bundles" etc. Have a subtitle "Added Today" and have all the games under there.

I'm pretty sure they already did that in the second last big sale or so, but in the last one they changed the formula again.

IMO, continuous additions of new offers only work if all of them are prominently displayed at the front page and in such a way that they are clearly distinguishable from all the older offers. Or if I get notifications that titles from my wishlist are newly discounted and when I click on the notification, those titles are singled out. Instead it just directs me to the wishlist and I'll have to check myself what offers might be new. The front page mixes old and new offers. And many games that are discounted are not even mentioned on the front page, I think. All in all, not very customer friendly. I don't like this approach in general, but it's made worse by GOG's lack of good filtering options.

it's rampant too

looking for games on your wishlist by price, the options are:

free
discounted
25+
under 25
under 15
under 10
under 5

this is bad for so many reasons, but, isn't something that is under 10 also under 25? etc?

I can't imagine it being done in a worse way

and I can't figure out how they can't be trying to have a shittily non-intuitive functioning site, like netflix, they have the stupid-bug

deleted

I'd already be happy with just a single option: sort by price.

Anyway, we already know they are ... working on replacing (some? of) the system, and that will happen ... eventually (in other words it won't change anytime soon), but IMO if you're already aware of these flaws, you should avoid anything that makes them all the more obvious.