My wife and I hiked in Glacier a few years back on 4-5 trails by ourselves. Apparently there has never been a bear attack on any group 4 or larger in the park. That is why the recommendation is to hike in that size group. While hiking alone, we didn't have an issue. Most trails have numerous people on them. We carried bear spray (highly recommended) and made noise as we approached blind curves on the trail. You can "hook on" to another small group by asking if they mind if you hike with them. If you stop, just look for another group. Don't let your fear of a bear attack keep you from doing what you want!
