Inside SoftBank Group Corp., the idea of going private through a buyout has been discussed off and on for at least five years. Almost everyone except founder Masayoshi Son opposes it, people with direct knowledge of the matter have said.

The reasons are substantial: No one has pulled off a buyout anywhere close to SoftBank’s ¥14 trillion ($130 billion) valuation, it’s not clear the company could raise the necessary financing and such a complex deal would prove a distraction for at least a year, the people said. Senior managers also worry that without public shareholders, it would be harder to keep Son’s wildest impulses in check, one person said.

That doesn’t mean a deal is out of the question. The conglomerate considered buying out shareholders and retreating from the public market again this year, the people said. Son has been frustrated that SoftBank’s market capitalization continues to fall far short of the value of his holdings, particularly Alibaba Group Holding Ltd.