Why is alternating kick and snare so common in beats?

To answer your question, if the snare and the kick were to be played in unison all the time, they wouldn't be able to create variety of contrasting rhythms, hence alternation is necessary.

1. Should kick and snare be same volume?
2. Why is the snare on 2 and 4?
3. Can a kick and snare hit at the same time?

Should kick and snare be same volume?

The snare is the foundation of the backbeat, and typically one of the loudest elements in the mix. Next, bring the kick fader up until it sounds almost as loud as the snare. It should be loud enough that the low frequencies are rich and powerful, but not so loud that it masks the bottom-end of the snare drum.

Why is the snare on 2 and 4?

Snare drum

The kick's main compadre, the snare is higher in pitch, with a fundamental frequency usually around 150-300Hz. ... In most genres, the snare is found on beats 2 and 4 (the backbeat), providing a sense of push and forward motion.

Can a kick and snare hit at the same time?

As a general rule, yes.