Hexblast trickster - Why pick up +1 curse?

Hey, I m checking out these builds on Poe Ninja and most of them dont even run one curse, they use wither with totems instead, so why do they all pick up the +1 Curse notable??
I m using temp chains with blashemy for now (HCSSF), but I still dont see how would I utilize an additional curse.

Please someone who knows answer me, so far my best guess is ppl are just blindly following other's skill trees.

You need two curses because:

1) You must have an aura curse (blasphemy or profane proxy) for clear, otherwise if you hit a mob and one shot it, it wouldn't get the hexblast explode and your clear is terrible.

2) You must have an on-hit curse, because aura curses have a cooldown for refreshing after they get removed, about 0.25 seconds or something, which is NOT fast enough for bossing. On-hit curse will immediately reapply after every hit.

If you're ONLY bossing then you can drop the aura curse

Thx for the info! I m still a bit baffled cause those builds run 0 curses, but at least I know how its supposed to work, ty.