European low-cost airlines are terrible. They do everything they can to lower the fees they pay. That often involves skipping major airports, unless they can negotiate a cheap enough deal with the airport. Those deals tend to involve things that make the passenger experience worse, because the airports don't want normal airlines to choose the same deal.

If you choose a normal airline and fly to any reasonably big airport that's not overcrowded, you'll get a jetway outside exceptional situations.

I've flown on major airlines through German hub airports and was stuck riding a bus to the airplane.

A decent new airport or significant airport reconstruction costs probably $5B+ (DEN cost $4.8B in the 90s; Beijing Daxing cost $11.5B) In austerity-minded Europe there really isn’t money for this. Even if there was, NIMBYs and green campaigners mean there is very little appetite to pursue it politically.

Oh, we have them, but they charge extra for it. Capitalism, you know.