This idea has been merged with Remove pre-requisite of ArcGIS Online/Portal for Web AppBuilder.
I would like to propose the ability for the Web App Builder to let you connect to a REST Endpoint Map Service instead of having to go through ArcGIS Online or to install Portal. It adds another level of complexity that is really not needed. We already connect to AO through REST why not just go directly to REST. Our more novice users like to user AO, but for us we would just like to connect directly to a map services through REST. It seems it can be done since you can connect to Geoporcessing, Geocoders and print services in Web App Builder so why not map services as well.
When something breaks in the website you just have something more you need to check which is AO or Portal being involved as well.