I always use Wifi and I never had a problem.
And if you are really serious about Ethernet you already own a dongle... jeez, it's $15. Don't make a huge fuzz about it. You always need to buy "something" to get the max out of your console.
Also, not including an HDMI cable with the 360 in 2005 was a wise decision as no freaking person back then had an HDTV yet. Same goes for the Wii U: Most people use WiFi. No reason to make the product bigger and more expensive just so a minority of customers can have their 10% more stable connection. It is called being a business and serving the customers. If only 10% of your customers want something you don't add costs for the other 90%. You are not the center of the world.