The sages can.
For us, unenlightened people, it is not advisable to meddle without being asked.
Why? That is how the Buddhists practice respect and patience. We have profound respect others and therefore respect their decision to suffer instead of asking for help or accepting our help. We also practice patience by enduring it, knowing full well that it may hurt deeply too from watching their senseless self-torture, but choose to patiently wait until they are ready to ask us to help. To force help down their throat may not work and might destroy our chance to help them in the future.
Having said that, there is another way. Get them a Medicine Master Buddha plaque or vigorously do things to create blessings on their behalf. When they have enough blessings, they will no longer have objections to your help.