Tennis- the Game that "Aint On Time"

This being that time of year where there are quite significant Tennis tournaments in the local area (New Zealand & Australia). All the big name players are in town, or across the ditch at various feeder tournaments that build up to the Australian Open. Tennis was once the sport of kings, on par with Equestrian racing and football.  Now it has many other sports to compete with in what is the modern marketplace of television rights, advertising sales, merchandising and putting bums on seats to fill stadiums. An utter snake pit where games can be held for seconds, minutes, even moved to ungodly hours of the morning or night to benefit offshore broadcast markets. Players are sometimes put at the mercy of this multi trillion dollar business - that is professional sport.  Lets face it, most professional sports that bring in the big bucks have a ethos that evolves around the clock, prime example being football which is the sport that has the highest net profit each year- running off the clock at 90 minutes, plus added stoppage time give or take 1-10 minutes as determined by the referee's assistant.  So where is tennis lacking where other sports prosper?  To become an elite tennis player is no easy task, these players are incredible athletes that required years of training just to even reach the world tour. Only exceptional talent there on in gets them to the purses that net sometimes millions of dollars- PER TOURNAMENT. Yet, games can sometimes drag on continuously without merit to the sport itself. It is great to see games that can continue onwards throughout the evening, even into the early hours of the momring- however this should be kept to team sports only. Putting an individual through that strain of absolute competitive effort for sometimes (going by the world records) a day and a half solid because of the meaningless tie-breakers. Time after time with only small exception, the player that has an extremely long and drawn out late-night game that goes into the early morning tends to lose their next match. This is down to one thing, the player is tired, far more so than their opponent that may have only had a straight sets victory.  This brings to light the issue of time. Quite simply put, if tennis were played on a set time limit then players would prepare for games knowing how long they were in for and another competitive streak would come out in them in the closing stages of the match knowing they have only so little time left to save themselves- as you see in stoppage time in football.  We should see matches of which a time of possibly 2 hours is enforced. With finals being 3 hours. Obviously the debate on how long these matches would go would be a debate that would go on for years, and be changed numerous times.  Yet, players would be more protected, broadcasting rights would be maintained and advertisers would be able to sufficiently plan their projects around games that would seemingly only go for a set time. Officials and tournament organisers also would be fresher off at the end of the day, only having to officiate at a far less strenous schedule.  So, why is Tennis not run on the clock?