Statement: This post is only the personal view of the author and does not represent the opinions of ALLPCB.com.
Via is just one of the parameters you can use to tweak the
autorouter. Via add a little cost in drilling, they take up
space, and other things being equal and it is better for a route to stay on the same layer.
The use of via has both advantages and disadvantages, it depends
on your choice.
I wouldn't say that via is not good, sometimes can be used as
good for us.
I think the reason is that vias could occupy significant
space from other components, so that the size of the PCB need to
be bnigger, which will cost more.