>>715100274I kinda feel like that's just something you inferred from otherwise extremely little characterization. Sonic 3 takes place immediately after Sonic 2 so it makes sense that Tails was still around. These characters didn't really talk prior to SA1 so Sonic and Tails "being like brothers" is largely sort of headcanon, at least where those original games were concerned. Naturally, SatAM and the Archie comics milked the idea for all it was worth, but in the games, very little was stated concerning the nature of their dynamic.
Also, it wasn't until SA1 where Sonic started his whole "eternal nomad" schtick. Since Sonic had almost zero backstory in the classic era games, for all we knew, he DID have a permanent residence. But from the Dreamcast onwards, it's established that Sonic never stays in one place for too long. He's always traveling. So it does make sense that Tails and Sonic aren't always together. Tails is an inventor, he can't be constantly on the move like Sonic is. He needs equipment, a lab.