Raspberry Question!

On the way to a family celebration we stopped of at a local garden centre and somehow managed to spend thirty pounds even though we were only looking.
We bought five canes of Raspberry All Gold amongst other things. On reading the label it states not to grow them where Rasperries have been grown or anywhere you have planted anything of the Genus rubus.
Why is this? I was going to plant them in an existing Raspberry run.
 

Rubus is a member of the rose family and so is susceptible to replant disease - this is what the RHS has to say on the subject

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=572