This is simply because the costs of following politics are large - it arouses negative emotions such as anger or depression - whilst the benefits of doing so are small; it’s not as if you can do much about the failings of our political system. Utility maximization, then, urges us to ignore politics.
So, what would be wrong with someone who avoids, as far as possible, all political knowledge - they don’t buy a newspaper, ignore political websites, don’t watch TV news, turn off the radio when the news comes on, and so on?
The obvious answer is that paying attention to politics isn’t a matter of narrow utility maximizing. We should do so because virtue requires it. Being a good citizen requires us to follow politics.
But does it? There’s a long tradition of people shunning public life: monks, hermits, Voltaire advising us to cultivate our gardens, MacIntyre urging us to retreat into local communities. And what’s virtuous about wishing to impose one’s own ego and limited knowledge onto the rest of society?
Nor is it the case that ignorance about politics need, in principle, be associated with general ignorance or incuriosity. It’s perfectly possible in principle to be very informed and cultured on all sorts of matters whilst paying no attention to politics - just as one can be clever and cultivated whilst being ignorant about, say, fruit flies or medieval plainchant*.
So, shouldn’t we consider the feasibility and desirability of opting out of interest in politics? Of course - to paraphrase Trotsky - we might not be interested in politics, but politics is interested in us. But it doesn’t follow that we must reciprocate, does it?
* This is not my own position. For me, there's a close parallel between politics and stock market investing, in the sense that both are interesting not as things to do, but because they provide us with ways of studying human behaviour. But I can fully appreciate that people needn't share my intellectual tastes.