Why is Figma/Adobe XD needed?

A bit about myself - I'm an 18 year old amateur graphic designer who works primarily in Photoshop and Illustrator. I've also been trying to learn coding for the last couple of years. I have developed a few basic games in Unity, have learnt a bit of basic frontend dev, and currently I'm learning Flutter.

My question that has always puzzled me is, why do we need UI/UX design software such as Figma/Adobe XD/Sketch?

I've never felt the need to design a mockup in Figma first, and then replicate it in whatever app I'm making. Or even if I do need a reference, I've always just used Illustrator to design it. I just can't get why UX design software is needed.

I'm not hating, I'm very new to this, and I'm simply trying to understand the use cases.

Thank you!