[[[
very moderately because I don't want to offend anyone and apparently some earlier postings, mine probably, seem to have offended some]]]
the one frequency monitored 24hrs/day is 121.5
Yes, and I appreciate one should call them early rather than late. But - on a general note, and without wanting to make ANY assumption about the present sad case - there have been situations where woe came up so suddenly that no time was left for ANY radio call. Radio is only the third point - aviate - navigate - communicate, remember - so it is important that our whereabouts should be known at all times. For this purpose, OCAS an information service seems best placed.
And BTW, for us microlighters the 24/day bit is rather irrelevant, we're not supposed to fly in dark.