I really think this depends on the type of cinema, the type of film and the time of day. A popular blockbuster movie suitable for the family will have a food and drink problem, and evenings probably too.
We go to weekday afternoon showings (Silver Screen if possible) and everyone sits quietly, doesn't make either noises or smells and I've never had the slightest problem!
My only complaint is the cinema volume level which is extremely high. I had to take concert earplugs to My Generation, A Star is Born and Bohemian Rhapsody because they are all musical films and it was deafening! It could be that particular cinema of course......