In a city with houses this established, drains have been in use a long time, and a lot of them are overdue for more than another snaking. The pattern may sound familiar. Drain clogs, plumber snakes it, everything's fine, then a few months later it's slow again. That's not a scam and it's not bad work. A snake punches a hole through the clog, but the years of grease, soap, and buildup coating the pipe stay right where they are, and they close the hole back up over time.
Hydro jetting breaks the cycle. A high pressure stream of water power washes the inside of the pipe, wall to wall, the entire run, and carries the buildup out of the line.
Not every drain needs it, and nobody here will tell you otherwise. Sometimes a snake is all it needs. The contractor looks at your actual line, gives you the straight read, and recommends what makes sense. You decide.