Walking down a residential street after dark and seeing straight into lit living rooms is one of the first things visitors notice, and it usually gets filed away as inexplicable rather than asked about. There is a history behind the bare window, and a social convention that makes living with it workable.
Partly religious history, partly practical. The bare-window habit traces back to Calvinist culture, where having nothing to hide was a visible virtue — closed curtains implied you had something to be ashamed of. Add a climate with long dark winters and grey skies, and there's a real incentive to let every bit of daylight in rather than block it. Historically, big street-facing windows on canal houses also signaled that the household had nothing to conceal from neighbors — and, for merchants, doubled as a way to show off the furniture. The social contract that makes it work is that staring into someone's window is considered rude, so in practice nobody's actually watching you eat dinner even though they technically could. Expats usually find this deeply strange the first few weeks and then either adopt it or compromise with sheer voile curtains that let light through while blurring the view. Ground-floor apartments on busy streets are the main exception — plenty of people there do close up in the evening, practicality beating principle.