There’s something called “The Rule of Odds” in design, which states that visually an odd number of items are more appealing than an even number of items.
Why is this, and why does this usually manifest as 3 items, rather than 1, 5, or 7 items?
First, I speculate the appeal of three items has to do with the neurological difference between contrast and balance.
Whenever you place two or any even number of items together, this often results in comparing and contrasting these even-numbered sets of items, something which feels like an active and aggressive mental state. However, when evaluating three items together, it feels like we are seeking balance instead, a more relaxed mental state.
Second, of the odd numbers, I think 3 is generally chosen to represent balance more frequently because the balanced grouping of 5s, 7s, or more is just too complex. (The number 1, also an odd number, is a special case of balance—unity, balance within itself—which has a different type of appeal. For example, a single point is much different than a triangle!)
So, when I am trying to generate something creatively appealing (and something which suggests balance) I usually go with 3. It’s a simple trick, but one that usually works.