I suppose it would depend on the rebel. Leia, for example, was a prominent member of the Imperial Senate and wouldn’t have simply been murdered, and Mon Mothma didn’t have to flee until she publicly spoke out against the Empire, despite having helped organize the beginnings of the Rebellion long before that. As well, it’s near impossible to track a ship through hyperspace, and any rebel hoping to visit their homeworld (as long as the spaceports were not being actively monitored by the Empire) could easily avoid being followed by making a few jumps in different directions. Not only did the Empire lack the resources to establish a presence on all the famous rebels’ homeworlds, plenty weren’t exactly friendly to the Empire, and a number of the more powerful systems were essentially allowed to govern themselves. Corellia, the birthplace of many famous Alliance pilots, including Wedge Antilles, was in a situation like this.
Hope that helps! If there’s someone specific you’re wondering about, feel free to send another ask.
~ Jacen