RetroGaming

It wasn't a case of "why bother," it was a case of evolution.

The original intent of arcade video games was to obtain a high score. You played until you died, and the game progressively got harder until you choked, or it hit some arbitrary limit of difficulty and went on forever, or in some infamous cases (Pacman) crashed. These video games were a conceptual extension of the arcade games that existed before: Pinball machines. Pinball games don't have an end state, you play indefinitely for a high score until you choke.

Arcade video games could have endings, and even though in the very early days they didn't: Crystal Castles was probably the first, in 1983. Even then, after reaching the "end" the game would loop so you could play it indefinitely until you died. Because that's how arcade games worked. A lot of games starting from the 1990's and beyond had endings of some description or another because they were in some way narrative based. In most cases (with the exception of some 1 on 1 fighters) you can still play another loop after the ending.