To some players…
Multiclassing as a kind of sin. Taking a multiclass is a temptation. It’s not something you plan. At one point you are leveling up and just walk over to the wrong trainer, like visiting a *****, and take a dip into a new class. Keeping their class pure is like guarding their virginity. They feel there should be a reward for staying pure. Taking a second class is like having an affair. You get a short-term thrill from the new abilities the second class brings, but in the long-term you regret the second class because you have damaged your long-term relationship.
For other players…
Multiclassing is a discipline. They plan their levels carefully. Often the splash class lowers their BAB, which hurts a low to midlevel fighter. They slow their advancement in spell levels, which hurts a low level caster. They balance their stat allocation at start, which hurts at first, but over time is compensated by their level-ups. In the end they have a multifaceted, self-sufficient, more entertaining character, which is also unique and feels like their own design and creation.
So which are you? Is multiclassing a sin or a discipline?