There are some very prominent architectural photographers who use no supplementary lighting with excellent results. However, they will wait for the time of day when the ambient lighting is optimum and may spend considerable time controlling and shaping the ambient lighting. Also, they may often spend hours doing post processing for each image (or pay someone else to do that for them).
Sure, but what if it is cloudy?
Of course sunlight comes through the windows and can increase the contrast, but that does not always happen. More often then not, the weather just does not cooperate, or the windows face north. Instead of direct sunlight, you get indirect, which is just as flat and shadowless as ambient interior light. Or, lets not forget, that direct sunlight is usually so strong it drowns out all the nuance of the interior ambient light, which produces almost just as flat an image as without it.
So should someone hope to be lucky and relish when he/she is, but accept that more often then not he/she won't be? That does not sound very proactive to me, nor something to build a reputation on.
I look at so many interior images nowadays, that rely solely on ambient light, and they are simply flat and dead. Yes, they are exposed well with nothing over or under, but that does not make a great image. Light and shadow and contrast does, and if your light is flat there ain't nothing you can do to fix it.
Although it may be part of the style of some photographers, I admittedly disagree and oppose telling those whom are just starting out to rely on it and use it as a substitution for lighting.
Really, it is beyond my comprehension. No serious (table top) still life photographer would ever agree that one could survive on ambient light alone. However, many (large scale) still life photographers, aka interior photographers, somehow think you can get away with only using ambient light.