Live bloodworms are easy, and my bettas really like them. Blackworms and brine shrimp would also work, but I've never fed them to my bettas. I don't really think their a big deal to use, but some people don't want to bother with them. Bloodworms are cheap (couple bucks, $2.79 from my lfs), and will last up to 3 weeks in a little cup kept in the refrigorator. I never end up using the whole cup before they go bad, so I just throw the rest out when they start looking discolored or smell... not so fresh. Just use a toothpick or paperclip to drop a couple into the tank at feeding time. I use Hikari Betta Bio Gold pellets in the morning, with live bloodworms (or frozen if I run out) at night. One of my females actually jumps out the the water for pellets in the morning at feeding time. All my bettas are very active and healthy, have great color, and regrow torn fins at super quick rates.
Live worms should not be a staple.