Here are some key reasons for the rising popularity of hand warmers:

1，Portability
Hand warmers are lightweight and compact so they can be easily carried in pockets or bags. Useful to have on-the-go heating.

2，Targeted Warming
They provide direct warming to just the hands unlike heating the entire body. Ideal for cold hands.

3， Outdoor Activities
Very handy for maintaining hand warmth during winter sports, hiking, hunting, camping, etc.

4， Improved Circulation
The warmth improves blood circulation in hands preventing numbness and supporting dexterity.

5， Arthritis Relief
The mild heat helps provide soothing relief for joint pain that worsens in cold weather.

6， Emergency Warming
Hand warmers can provide critical warmth in unforeseen situations like car breakdowns.

7， Affordability
Highly economical compared to heating devices with most under $20. Also reusable.

8， Safety
Flameless operation removes fire hazards associated with traditional warmers.

9， Easy to Use
Simply open the pack and insert in pockets or gloves. Provides hours of warmth.

10，Variety
Available in different types like chemical, electric, charcoal, etc. to suit preferences.

In summary, hand warmers conveniently provide portable, focused warmth in an affordable and safe manner. Their versatility makes them a winter necessity for both everyday use and emergency situations.