It also makes sure all the beat dependent effects are applied correctly to said tracks. It also works as an anchor for quantization, loops and beatjumps.
I dont really get what you mean about them only setting the average bpm, what kind of music do you play? Traktor is used mostly by people playing electronic music (duh) which in 99% of cases will have a consistent bpm throughout the track. Obviously if you try to beatgrid a punk song for example, there would be problems, but none you wouldn’t face from any other method of trying to mix that style of music.
The thing is, the grid is purely based on mathematics - you input the BPM (or traktor guesses it) and the first beatpoint, and the grid is just a factor of the BPM and the amount of time that has passed in the song. So it has to be an exact BPM to work properly, and if the song changes BPM you have to do workarounds to use the gridding feature. It’s generally better to ignore grids and just mix by ear when you have such songs, unless you are willing to spend some time picking out loop points and setting cues there, which can allow you to do some more complex things.
In Ableton, when I create an 8 bar loop, I know that with properly set warp markers, that 8bar loop will be perfect every time - no matter how far along in the track that loop is set.
Can Traktor do that - I’m thinking in the case of tunes (Hip-Hop/Breakbeat, etc… - all constant BPM stuff) that have been ripped from vinyl.
That’s the up side of Ableton; warping sorts out all tempo variations once you’ve accurately set markers, timestretch algo etc. Beatgrids can’t correct tempo fluctuation like Ableton but on the other hand setting Beatgrids is a lot quicker than setting warp markers. Traktor/Beatgrids work well with solid tempos. Ableton/Warping works well with variable tempos.
Two different animals really. Other factors like workflow come into question … depends on what works for you.