Chapter 2 starts with discussing Pythagorean triples (PT), which is an ordered triple $(a, b, c)$ such that $a^2 + b^2 = c^2$.
It further shows the existence of an infinite number of such triples, by showing that given $a^2 + b^2 = c^2$ and some $d\in\mathbb N$, then $(da, db, dc)$ is another PT, and shows a simple proof.
Then it states:
Clearly these new Pythagorean triples are not very interesting. So we will concentrate our attention on triples with no common factors. Primitive Pythagorean triples (PPT).
Why are PPTs more interesting? I understand that these are going to be rarer, but do they have some sort of application that regular PTs don't have?