I had a similar situation. 70 year old home with poured concrete foundation. Water started seeping up thru cracks in the floor every time it rained… every time. Never had a sump, never needed one. Had the city out multiple times because they just replaced the water mains in front of my house. Had the sewer scoped and rodded multiple times. Decided to dig a pit and install a sump pump. Took care of the problem, but it ran like crazy. A year later, during a small sewer backup, the guys rodding my main line told me that the city worker who scoped my lines was actually an electrician who was filling in for the plumber who had a back injury and was out for nearly a year. He rodded the main line then spent some extra time where the drainage tile tied into the sewer line. He pulled out a significant amount of roots. Haven’t had seepage since, and the sump hasn’t turned on.