Overall people have proven themselves too irresponsible to save for retirement. Just look at the baby boomers - many of them have houses, cars and have had great careers but very little or not enough savings. When people get raises throughout their careers they tend to use it to buy more stuff and increase their standard of living (vs. Actually saving for retirement). Retirement is often a low priority for people until it is much too late.
Some are entirely capable of preparing themselves for retirement while some lose track of time and it sneaks up on them, it's entirely a case by case sort of thing. I'd say more people are likely to make mistakes saving than people that won't, but there's certainly people in both groups.
Most people don't even start saving until they are already 40 or old which is way too late, others believe they will rely on the government when they age. People want to spend their money to have the latest gadgets and the biggest homes without thinking about their or their children's future.
It's not irresponsible, it's nearly impossible. Most of us are struggling to make ends meet right now, let alone save up to make ends meet later. This economy sucks, and we all know it. The statistics for people who can't even afford to move out of their parents house is very high right now, because they simply cannot afford it.
No not all people are too irresponsible. Some people naturally plan ahead and think about their future so they have enough saved for retirement. Sometimes even their jobs and careers may offer a retirement saving plan for their employees. I know this because that it how it is in my fathers workplace.