Some things are necessities, some are luxuries. A basic law of business says you sell luxuries to those who can afford them. Necessities are sold to everybody, because we cannot live without them.
Self-defence tends to fall through the gap of this type of thinking. We couldn’t consider it a luxury, but nobody considers it a necessity till they need it, or till they perceive a potential threat. Like anything concerned with safety it probably should be considered a necessity; we need to encourage its wider adoption.
Learning a martial art is one way to indirectly deal with the issue. Individuals learn the martial art as a sport, and acquire some self defence capabilities as a side effect. Sport is something of a luxury item, we don’t absolutely need it. But if it encourages a healthier lifestyle is has done more than enough to justify the time and money spent. And if it does help us in a crisis, may that never happen, then that is an added benefit.