8 Obut boules in a wooden box

Why sets of 8 boules if the rules say that teams of 2 players
use 3 boules per player, thus 12 total?

In the old days in France, there was no such thing as "sets" for multiple players. Every player had his/her own 3 boules. The same way a tennis player has his own racket, and a bowler his own bowling ball. When game time came, each player would use either all 3 (for singles and doubles games) or only 2 (for triples games). Simple, straightforward.

But come summertime, when the Parisians and numerous other tourists flooded the South, they had no boules of their own. Stores were clamoring for "instant" packages to sell to the new petanque converts. Easy to carry, easy to sell.
Six boules (2 x 3) would not be enough for a family. Twelve boules (2 x 6) is hard to package and quite heavy.
So the French manufacturers came up with a set of 8 (4 x 2), similar to your typical "bocce" set. Ideal for Mom, Dad & two kids. Or for two couples.
A hybrid so to speak, based on practicality rather than traditional rules.

Is a set of 8 boules right for you?
If you usually play with 2 or max. 4 people, and/or like an easy set to toss in the trunk, absolutely.
If you expect more than 4 people to play, go for two sets of 6, or a bag of 12.
Or two sets of 8, of course. Then up to 8 people can play!!

The more boules, the more fun.