I live on a +25 'Beautiful Vista' lot in the hills in bridgeport, in a half-glass house (approx. 75% of walls are glass). At first I would get the moodlet while in the house, but after I made it slightly bigger (by 10-20%), and added a fence and a celebrity gate, I lost the moodlet inside the house, I still get it once I go out on my lot. Why did I loose it?
The Beautiful Vista moodlet is Deep Magic; and it's never been entirely clear how it works; but it seems to require whatever the game calls an unobstructed view.
Most likely this means that the moodlet will only be given:
Note that this is just an educated guess, and code spelunking might be required to figure out the exact parameters.
'Beatiful Vista' is a moodlet you get when your sim lives on 'prime real estate'. Think Boardwalk and Park Place from Monopoly. Certain high end lots get this assigned to them based on their location, usually a flat piece of land, high up, with an unobstructed view of the town.
I dont know why you lost it, as the moodlet comes from the lot itself and not from anything added to it. You could level the entire house and walking on the grass would/should still give you the moodlet.
Also, decor maxes out at +40, unless you are 'over emotiona'l and 'eaasily impressed', then it (and most other things that bring you joy through moodlets) will be +50 (+5 for each trait)