I don't fly very often, just for vacations, perhaps just a couple of trips
to North America (GLA via LHR) every year, and maybe once or twice
from GLA to LGW or somewhere in Europe, all on the cheapest fares I can get, although when I go to North America I usually go WTP.

So I'll never be a silver Exec Club Member.

However, quite often when checking in at GLA I'll be informed at
check in/bag drop that I'm welcome to use the BA Lounge.
I've never queried it, but just been grateful to use the Lounge facility,
as I've read on here and on the BA website that Blue members like myself aren't entitled to use the Lounge facilities.

Would there be any particular reason why they offer me this facility on
certain occasions?

Thanks
Gorcat