Tree roots growing into sewer lines is a common problem. Roots crawl into tiny openings and expand in the sewer line, latching on to other debris that typically cause backups such as grease or eggshell waste. Sometimes chemicals can kill the trees roots but if the roots reappear, the pipe may be damaged and require excavation to fix the problem.
Homes that were constructed prior to city sewers often relied on cesspools. After cities installed public septic systems, sometimes the cesspools were left intact and connected to the sewer line. You won’t know unless you inspect the sewer.
Many homes built in the 1950s have sewer lines made from tar paper called Orangeburg pipes.
These disintegrate and collapse over time. If a home has Orangeburg, the sewer line definitely needs to be replaced.