When you arrive in somewhere like the Norway or France, and go to leave the baggage area, you'll find yourself with a choice of two lanes for customs. One will be Red and labelled something like Goods to declare, the other Green and labelled something like Nothing to declare. If you take the red lane, you'll need to speak to a customs officer. If you take the green one, then you'll walk past customs officers (possibly behind a one-way mirror), but unless they decide to check out, you'll keep walking and won't speak to anyone.
With some other countries, such as the USA, Australia and India, before you can leave the customs area you must queue up for a customs officer. Depending on the country, they might take a form, or they might ask you some questions, but you'll have to wait to interact with them, even if they then direct you to exit without further checks.
For passengers, the first style of customs is much more preferable, as if you've nothing to declare then you can often exit the baggage area through customs in seconds. For passengers, the second style of customs is much less popular, as even with nothing to declare you might end up waiting a long time (30+ minutes not impossible in the USA) to see a customs officer who then waves you through.
Why do some countries opt to make passengers wait, while others are happy to let passengers self-identify if they need checks + use random & targeted checks to catch people not properly declaring?