It is unlikely they will ever get a visitor visa with their overstay history and ties (you) to the US. If they do not want to immigrate then no, petitioning doesn’t make sense .. but given that you are considering petitioning for your mother, it’s the any possibility that they may want to immigrate in the future. The process for them will take 20 years until a visa is available .. filling a petition now and letting it sit for that time is sometimes chosen as a safety net that’s then ready IF they want it later. Your decision