Getting a community nurse or anyone else to come over to inject 4 to 10 times a day, at different times each day isn't very practical.
Insulin use in T1's is very dynamic, and depending on countless factors. It's not as if you can just have someone inject a fixed amount twice a day and that is that.
Being able to do your own injections is the difference between being very dependent on outside help, losing all opportunities for spontaneous decisions, and leading an almost normal life.
If I take myself as an example, I may wake up at 5AM to see I need some insulin, even though I usually don't need it until 8. I can just take half a minute to inject and put out the light to sleep for a couple more hours.
But what if I'd need to call someone to come over to give me that injection? No more sleep in that case.
Or say my neighbour asks me to come over for a cup of tea. Can't do that, because the nurses visit has been planned at that time, and I'll have to eat right after her visit.
Or the nurse has been for my pre-meal injection, and it turned out I needed a little more insulin for that meal.
Can I call her to come back two hours later to give me some more insulin?
Believe me, being dependent on outside help for your insulin is a nightmare any T1 will want to avoid at all costs, if in any way possible.