Cannot say why decimal time didn't stick, but a similarly-proposed semi-decimal calendar with 12 months of 3 weeks each of 10 days was abandoned in France solely because Napoleon didn't like it.

It was also designed to frustrate Sunday church attendance because Sundays being every seven days would usually fall on a weekday on a workweek based on a ten-day week. While Revolutionary France experimented with state atheism and then deism, it eventually returned to Catholicism.

France spread its decimal measurements (the metre, gram, and litre) to the countries that Napoleon conquered or tried to conquer, but by that time, France was well beyond the "stamp out all semblance of religion" phase of its revolution, so a calendar designed with the intent to stifle religious attendance in mind was never going to stick very long once the French had left those territories. Besides, doing maths on length, volume, and mass is something that people do far more often than performing those calculations on dates. Sure, it would have made some things more convenient, but I'm guessing that for most people, the ten-day weeks just stuck out like a sore thumb.