Why blazor use signalr ?Compare to grpc when should to use signalr or grpc?

Question

I do not think the web need use real-time communication,but blazor do use signalr why?
If there is a scene that many users will get the same order which to use is better?
let me say.
If there is a order list that is user1 or user2 send

order01,order02

and other user will grab the order then other user can not see it.
if user05 take the order01 then other user only can see order02.but the user still can send new order.

for the two of signalr and grpc.I think both of them can do it.

1. grpc:I will call the client procedure to update the list which user
   can see.
2. signalr: I will change the list directly.

which is better?and why the blazor use signalr not grcp? is it is better than grpc?