The most common aspect ratios used today in the presentation of films in cinemas are 1.85:1 and 2.39:1OK, so with a 1:1.85 ratio the "notch" (otherwise known as the sensor area) doesn't matter. Now to address your other point, say you are watching a move in the other popular ratio of 2.39:1 here we have black top and bottom. Now if you were watching this on any flagship Android phone you'd still have space top and bottom whether it was a Samsung at 18.5:9 or the other Android phones at 18:9 you still not be using the full depth. Now if the movie is shown on the iPhone X and it is sized to not slip under the screen sensors then guess what, you'll be watching it on a ratio of 18.5:1 which is exactly what you get if the bezel was extended on both sides of the sensors.
Now if you say but if the sensors were not there then you'd have a 19.5:1 ratio and while you'd still have black top and bottom the image would be slightly larger. Now this begins to get a bit silly because if you removed the sensors and had all screen then the phone would have to be bigger to accommodate the sensors then Apple would put screen on both sides of the new sensor like it currently is, then you'd say again they should have all screen and this would continue forever until by the time the phone was 4 foot long you'd begin to realise there's a bit of a problem with this line of thinking!
To put it another way you are simply asking for a 19.5:9 screen ratio instead of the 18.5:9 that you get if you don't include the sensor area, but then you may as well say to Samsung, 'hey you made the screen ratio 18:5 why don't you make the phone taller and make it 19.5:9. Can you see this there is no validity in claiming the sensors take up screen space. Of course they do. Just like every other phone. However Apple has removed the bottom bezel unlike everyone else so really everyone should be complaining that Samsung, LG, Xiaomi and Pixel, should have folded the display under the screen and removed the bottom bezel like Apple have done.