I think you mean the wood finger boards, but in case you mean the metal table I'll comment on both.

Finger boards apply pressure on the strip to ensure the cove and bead is milled with precision. The slots make the board springy so it can accommodate the inevitable variation in strip thickness. The cove is really delicate so even a tiny fraction of an inch in variation will have an effect. Solid boards can't give like finger boards, so strips get stuck when too thick. (and no matter how careful you will get some strip thickness variation.)

If like me you haven't used finger boards before ripping strips, you'll be amazed at how effective they are.

The grooves in the metal table I'd guess are to reduce the surface area and therefore friction.

Hope I guessed your question right! My experience of ripping strips linked below

Cheers Ian

: What is the purpose of the angular lines that are cut into the guides on the
: router table (I'm not an experienced woodworker). I have seen it in
: several manuals and can't figure out the purpose.
: You can see them in the first shot of this video:
surface