What LittelRen says - there can be reasons why it is safer not to rush back for a landing...it sound very tempting to do that but it could be catastrophic.
Basically at take-off the aircraft (certainly a long haul one) will often be above it's maximum certified landing weight because of the fuel it is carrying....Now Boeing/Airbus etc will say it is possible in such circumstances from a pure engineering POV to return immediately to the airport and land straight away but there's a risk overstressing the landing gear, perhaps overheating brakes so doing that may not be without it's risks.
So, the teaching is (or was)..if you lose an engine on take-off firstly control the initial problem (fly the aircraft, secure the engine) and head off to a safe place. After that the flight crew (pilots) come up with a plan, usually after a discussion with ATC, company engineers and others involved.
99% of the time the plan would be to go through all that's required in a methodical manner, dump fuel to get down to landing weight, followed by a normal landing albeit on one engine.
A couple of other points, firstly many engine problems can look/sound quite spectacular to the passengers but actually aren't much more than a car backfire, or if they are an actual failure it's all usually contained within the engine structure - once the engine is shut down that problem is contained, done, dusted...A bang/flash doesn't mean the engine has exploded or you must rush to land.
The other point is with regard to time scale - with many "heavies" if you take off near maximum take off weight it can take best part of an hour to dump down to maximum take off weight, which explains the holding.
HTH