That's what has been done at Yellowstone National Park. All the tourist-accessible thermal features have boardwalks built out to and around them for both safety and environmental protection from the millions of vistors. Other features, like Old Faithful geyser, has been surround by cement paths and benches for visitors to view eruptions from. The backcountry, however, has no such facilities and people who visit those are basically on their own and need to use their own discretion. That said, people die in hot springs every year because they're too dumb to recognize the dangers.