why do people have so much games to trade but only want other games in return?

They not only trade them for games... they ll only trade them for profit. you offer one game they are even looking for, but they won't agree on a fair value 1 for 1 trade. you must offer more... like twice the value (be it current steam price or every game involved historical lowest prices). That's why trading is the worst occupation you could chose. And it's the reason why steamgifts works so well. People will rather just toss it away in a giveaway than going through the hell that is trading.

some people I think are like this but if you are trading games as occupation how do you make money? I did a few trades b4 not recent (not within the past 1.5 years) and it was ok I bought a bundled game and traded for a steam gift for another. Not sure how it is now but I see a lot of people with tons of games who only want games in return. How do they make money if they just keep trading games?

one - asking for money for them is not very easy to do or get

two - when bundles come out maybe people either have some of the games already or have no interest in them and therefore want to trade for other games they would more likely play

i believe this game is still on gamepass

Since the trade changes applied on steam a few years back, trading has been in a bad spot to make profits. Since now you have to rely in keys, not gifts. Gifts were probably the main reason to make profits with trading.

Other than this, actual profits in trading on steam comes from cosmetic stuff, like skins. Game trading probably has no profits or very small profits.

The only time i bothered to make profits with steam, was when they announced the card drop system, i applied to the beta early on, started collecting cards from the games i had and i started selling them. Back then cards were priced very high, like 30 cents to 1€ per piece, and there were people already invested in buying all the cards that early, i ended up making close to 80€ profit doing this before prices crashed down with the huge supply increase. I've made a few profits from small cosmetics in TF2 and some weapons.

I don't trade much, but got almost 500 keys in a list on ST. I mostly go for games in return, even though it is difficult to find stuff I want, because there is no figuring out prices, no regional transfer fees, no listing items on market, just decide if I want an offered game, and how cheap has it been compared to what they want.

After few years of buying bundles I had 100+ duplicate keys. I only recently discovered barter and traded about 100 keys already. I just trade to get rid of keys and have something for it.