You're right. Breaking up by ignoring someone is cowardly. It's also selfish and immature. But let's face it: Many people are selfish, immature, and cowardly when it comes to having to face a hard task.
No one likes to have to give someone bad news. It makes us feel bad. What people don't realize though that it is far kinder to give someone bad news directly than to leave that person with a million unanswered questions that will torment them for years.
The problem is that many men and women will fight a break-up. They want explanations or reasons to defend the relationship, and who wants to have to fight their way out of a relationship? Then, weaker personalities will try to hang on. "I'll be better" "Just tell me what I'm doing wrong" or "We can make this work."
It's important to use words that make it clear you want to break up and nothing will change your mind about that. "I'm sorry but it's time for both of us to move on. This isn't working for me but I know that there's someone else out there who is just right for you."
When the person tries to plea or argue, be firm and don't be tempted to tell him/her everything that you don't like about him/her. "It's best if we don't rehash everything or have to point out all the ways we don't work. It'll just make us feel bad. We're both adults and can do what's right and what's right is to appreciate the good things we had but move on when I am sure that this relationship is not for me any longer. It really has been good knowing you, and I wish you well."
You can even email, text or leave a phone message. It's tacky but better than ignoring someone.