Children have to function in the world around them. By y7, smart phones are a reality for things like catching a bus to school and accessing a school time table. They are practical tools for young people making the transition from child to adult.
My y6 has recently got a phone. The reality is that he was one of the last in the class and getting socially left out. He can now directly contact friends over arrangements like walking to school rather than going through chains of parents texting busy parents. He can now contact friends when they're geographically unavaliable to meet in RL because they're with their other parent/ extended family.
We don't live in Silicon Valley, there's a limit to my resources to manage my children's lives and fill their time without them having direct access to technology. They have to function in a compatible world with their peers.
I can delay to a degree. Better having a phone in y6 and being last than the first in y4. I can use parental controls. I can vet what they do/ access. I can create dialogue about what they do and what our boundaries are and why. Ignoring reality is damaging though, both socially harmful to isolate them too much, and doesn't necessarily prepare them for the reality when they outgrow protectionism.
When they were little and the world of teenagers having smartphones was fresh, I hoped that things might be better and safer than when mine reached that stage, but Pandora's Box is open, and we have to work our way around what emerged. Is it what I would ideally like? No. But I have to try and pick a moderate path with the best balance of benefit vs risk.