Strawberry spacing?

Hi.

I've read that they should be spaced at 18 inches.  But when you look at many successful strawberry growers rows of plants they seem to be much much closer than that.  Is there something I'm not getting here???

TIA

Adri

I've thought in the past that there's a massive difference between recommended row/plant spacing and what you actually see both on plots and commercial growers.

I'd like to know what the thinking is behind the very spaced spacing recommendation and what people actually use.