Problem with not having your own blockchain is that you depend on others,while you can make your own blockchain that fits your need perfectly.
And keep in mind that Agate blockchain will be POS and ethereum blockchain is still POW and it will stay like that for couple of years.But POS is future,especially for this kind of use
That is also big factor,POS is simply superior to POW and it is the future.POW is of course still good and can be good for some use, but for scalability,POS is better.
Thanks guys for extrapolating it for me.It makes sense now, didn't understand how big Agate network would actually be and that needs POS in order to work.
It does not really need POS to wor, but POS is better then POW. It is safer and more advanced, network can't be attacked by 51% attacks.