Can I assign the same keyword to more than one page?

Eazi-SEO doesn't allow you to assign the same keyword to multiple pages due to 'keyword cannibalisation'

No, we don't allow you to assign the same keyword to more than one page. 

This is because this could be bad for your SEO - it is called 'keyword cannibalisation'. 

The reason it's bad for SEO is because it confuses Google about which page it should show for that keyword. 

Google much prefer only one page for a given keyword, when it has two to choose from then you do not rank as high in the results.

Here's an SEO audit where it discusses the issue of cannibalisation and why it's bad for SEO in more detail, have a read!