It's more practical because it's less work than calculating consciously about what to do in pursuit of one's own self-interest in every conceivable human choice. The people who say or recommend that every moment of life be about "rational choice" are describing a living hell.
So people are more happy when they livng in a society with manners: When men know how to treat women, for example, and women know how to treat men. When holding doors and being chaste and even having, in even in other respects, clearly differentiated "gender roles" (a horrible phrase but you get my drift) is just a matter of what ladies and gentleman do. It's easier to live in a time when people have been properly habituated according to a shared conception of the good life.
In those times, people know who they are and what they're supposed to do. So they have the confidence to act well and even to display their cultivated individuality.
But those times aren't ours: The result is that people are anxious and disoriented and in some respects more lonely than ever. Because they don't know who they are, they don't know what to do. And so, to repeat myself, they can't find a standard higher than autonomy (or inventing oneself out of nothing) or productivity that gives them a point of view to resist the anonymous forces that surround them.
Okay: I know I'm playing fast and loose with what they psychological study linked claims to have shown. And I also admit that what's true about that study I knew before I read it.
One more thing: Practical altruism is sort of ridiculous. It's saying that altruism is in one's self-interest or not really altruism at all. According to Tocqueville, Americans love to explain that what they do to serve others out of love or instinct is really in their self-interest, They brag (falsely) that they never lose their heads, so to speak, to their hearts. When I read the linked psychologizing, my immediate response was there those Americans go again.