Why doesn't Cron allow for intervals UNDER 60 seconds?

perhaps because anything that needs to happen more than once a minute really ought to be its own process, governing its own schedule?

Like a daemon or service. That makes sense, but the instance that brought up this question came from trying to execute a PHP script every 10 seconds.

My solution was to create a loop around the particular process and invoke PHP’s sleep() function to pause it for 10 seconds. The script gets executed every 60 via a cron assignment.

You do make a good point, though. Thanks!