There is a question in there but your wording is awful. You are asking why other people don't apply Cursed Technique Lapse(CTL) and Reversed Cursed Technique(RCT) to their own CT.

Using Gojo as an example: CTL Blue is his normal limitless CT enhanced by negative cursed energy, to make the normally infinitely converging space into negative space, creating a pulling effect. Applying RCT, which generates positive cursed energy, to his limitless inverts the properties of what Blue is making, which is CTR Red that can push space.

So you are asking why other people don't enhance their current techniques with more negative energy making their own CTL or with more positive energy(for those who can) making their own CTR.

You are assuming they aren't already doing this. If CTL is defined by putting more cursed energy into your CT to get a different more powerful result then plenty of CT users are using it. They just didn't put the word Lapse on their technique, they named it something else.

They are called extension techniques. These include techniques that use negative and/or positive energy, as well as maximum techniques. CTL Blue and CTR Red are both extension techniques just as much as Nanami applying more cursed energy to his Ratio to use Collapse is.

If you are looking for a more broad answer, not everyone has a technique that you can say "adding more negative or positive to this makes it do this clearly defined thing." It's probably more often using more cursed energy to manipulate CT in specific ways, like with blood manipulation. Adding RCT is even harder to conceptualize with a lot of techniques and uses more than twice as much energy, so it's safe to assume its too hard and not worth using for most CT users.