they advertise it as low THC, low CBD 

i have two or three packs of them from freebies.but never looked them up to see what the levels of thc or if the they are sativa or indica .no wonder why they are giving them away.lpl

The real question is are you buying from Nirvana for free seeds or good genetics? Number #1 their prices are about the best. #2 When some of their stuff is on sale which almost all the time, the prices are even lower. Correct me if I'm wrong on price. #3 they been around over 20 years they didn't pop up out of nowhere like 75% of the banks out there now. #4 are they trustworthy, and try and resolve any issues. #5 they give away a free pack of seeds of your choice every week. I could go on but I think that is enough. Just some questions. I personally don't buy from them for something free. They aren't the only place I purchase. But some of the questions I ask myself before I purchase from someone else. A curious mind wants to know. 

Hey Rick no one’s knocking Nirvana been there for years gotten many seeds from them and never got anything free and was never looking for anything free I don’t buy discount I buy what I like and I pay for what I want so get off the defense side 

again my question is about the strain why would anyone want to grow a plant with such low THC and low CBD just because it’s free ?

It's mostly a land race strain so it hasn't been messed with genetically yet.  They are mostly so you can have a chance at breeding your own unique strains. If you look back at almost all cannabis genetics they all had low levels of thc and CBD respectively, before we all started breeding for better yields, heavier tricome and terpene production, and the desired growth structures of the plants.