Scheduled intervals are easy to officiate and completely indifferent to who is actually depleted on the field.
Drinks breaks arrive on the clock, not when players need them
The interval comes after a set number of overs, or at a fixed minute, or at the end of a quarter. It does not come when the fast bowler in his eighth over has stopped sweating. Officials cannot see that, and the rulebook does not ask them to.
Fixed scheduling is defensible as administration. Both teams get the same opportunity, the broadcaster knows where the break falls, and the umpire does not have to arbitrate a request. It is also, as a nutrition instrument, close to useless, because depletion is individual and the clock is not.
Watch what teams do about it. In cricket, fielding sides send out a substitute with drinks at every plausible excuse: a wicket, a review, a boot change, an over between spells. The laws allow refreshment during a stoppage at the umpire's discretion, and discretion is exactly the sort of tolerance that gets tested every match. Some umpires wave it through. Others do not, and the same side will be told to get off the field at one ground and be allowed a full team huddle at another, which is an enforcement inconsistency with a competitive edge attached.
Football is stricter and stranger. Players are not supposed to leave the field of play, so hydration happens at set-piece pauses, out of bottles lined along the perimeter, in whatever seconds the referee tolerates before he starts pointing at his watch. The result is a rule about time-wasting doing double duty as an unwritten rule about drinking, applied by feel.
I would rather the laws said what they mean. Give the referee an explicit discretion to grant a hydration pause on request, with the time added back, and take away the pretence that a player crossing a touchline for a bottle is an offence against the flow of the game. Add the seconds. Nobody dies of two extra minutes.
The current arrangement produces the worst version of both aims. It is not flexible enough to serve the athletes and not tight enough to stop the gamesmanship, and the deciding factor in any given match is which official happens to be strict about the boundary rope that day.

