100 points is not merely the "tournament standard," it is also the recommended point value in the rulebook.
If you play around with squad building it also becomes pretty clear that they intentionally designed the game with the 100 point squads in mind. Its also a really good balance point for getting a decent number of ships on the table while also progressing through the game efficiently.
Obviously you can play more or less as it suits you, but 100 points is a good standard for squad building and makes it easy to come to an agreement on point limits when playing with strangers and such