It would be incredibly useful to have, for example, two circles snap to each other not only at the anchor points but also at any point along the paths. This would help a lot when using Shape Builder tool, because at the moment most of the time you either get a tiny gap between the shapes (then the Shape Builder tool doesn't work), or the shapes overlap (then the Shape Builder tool leaves unnecessary anchor points which you have to meticulously fix).
Will Dinski commented
That this is still a problem (yet they continue to add new, buggy features) is why I won't ever fully embrace illustrator. They've had years to fix this.
It is really amazing how "Illustrator" the leading software in vector drawing (so they say), it lacks in basic functions, therefore in precision and simplification in drawing.
All vector graphics software have better management of point snaps, path snaps etc. (freehand 8, coreldraw, inkscape, Affinity Designer), NO Illustrator NO!
We should think about this!
Tautvydas, I agree that Ai should be able to to do it from the box, but if you desperately need it, try ColliderScribe by AstuteGraphics:
It does it brilliantly