Can one PayPal account accept payments for multiple online stores?

[des-Fontaines]

I am looking to start my store, and in order to accept payments I need to have an established business and other boring tax things. Now the question is, how does those youtubers have like 10 stores at once? Each shopify store is legally registered? Or I can accept payments from multiple stores to one paypal business account? 

P.S. Why on Earth Shopify cares if I pay taxes?