It's not really all that desirable to have explosives detonate at unpredictable moments. Not all these bombs are in rural areas, many of them are in the middle

It's not really all that desirable to have explosives detonate at unpredictable moments. Not all these bombs are in rural areas, many of them are in the middle of cities or otherwise in locations where it would be really really nice to warn surrounding citizens of any upcoming explosions so that they can make sure not to be nearby.