A common trend in the performing arts of the past 10 to 15 years is the omission of the interval. I don't think anyone ever did a poll of directors and choreographers why they don't include an interval, but I think the primary reason is that the interval is seen as disrupting the flow and integrity of the piece. I haven't done any comparative analysis on this, but it also seems to be a (continental) European thing.
The absence of an interval means that the audience is sentenced to sitting for two hours or more without being able to stretch their legs, go to the toilet or have a drink. After the performance, especially if it's one of those 3 hour mini marathon pieces, which today are not uncommon, there's usually a rush for the toilets.
A consequence of the absence of an interval is also that, if a spectator wants to leave, he or she has to disturb the performance. With an interval you just look at your watch, see that it's another 10 or 20 minutes until the interval and decide to sit it out.
Intervals also facilitate set changes. So unless the actors change the set, another trend, no interval means no set change. So why do directors and choreographers choose to restrict their creative freedom?
I should add that intervals can also be a nuisance if they're too long. At the Royal Opera House in London the intervals are sometimes longer than the pieces. Their purpose seems to be to allow the audience to socialize and the performance just functions as a conversation starter. Since I'm nearly always on my own I sometimes went to do some shopping in Covent Garden during one of those 45 minute intervals.