If you want to get hired on at one of the major Gulf operators or pretty much at any of the HEMS operators you must have an IR. The company I work for 100% of the pilots have an IR even if they are VFR captains.
As mentioned before it is mostly an insurance requirement but even if it was not, it makes good sense to have an IR as ones chances of surviving inadvertent IMC with 5-10 hrs of simulated is not that promising.