why was my kid in title 1 reading?

My daughter is older now, but I just have to ask...what are some of the common reasons why kids are put in title1?

In first grade my daughter was put in Title 1 reading. She was in until 4th grade. She just had a hard time learning to read. We'd read with her all the time and she'd have meltdowns. She went to preK. She had a supportive home environment. She still asks me all the time why she was in it. We were never in poverty (not even close). She just had a hard time learning to read. I believe in 3rd grade she scored on the verge of getting out, so she had to be in it in 4th grade. Isn't 4 years a long time for intervention?

Just looking back seems odd. All the other kids who were in it as well as her were just mediocre (including her) in high school. My daughter did well in college, and now in medical school, but wants a reason why she struggled so much. I guess she just kept scoring below grade level?, but why? There's all these tests they do for IEPs, but not for title. My daughter and I want answers. We're just confused. If they think she needed help with reading, could've just told me to hire in tutor, so I think there was something more going on there we just didn't know about. All the teachers I've ever talked to said she was doing "fine", but WHY WAS SHE IN INTERVENTION FOR FOUR YEARS????? It seems like every academic struggle she had she was "always on the verge". Always on the verge of getting out of title, always on the verge of getting an A.

It's just odd to me because some of the very smart kids were high all around and she obviously is very smart.