Lube is for unsealed chains.
All our modern chains have O-Ring or X-Ring or similar seals, that seal in the factory lube, to keep it where lubrication is required. You cannot add any lube inside those seals, so any lube you put on the chain is wasted and totally unnecessary.
So why do bike shops stock chain lube?
Because bikers ask for it! Why would they say no to a lucrative market?
But also because most racing bikes do not use sealed chains and they do need to be lubed frequently, so the dealers stock various chain lubes for that market segment. For adventure bikes, spend your money where its more needed.
If you want to give your chain some TLC, take it off the bike and soak it in diesel. Or brush some diesel onto the chain to clean off the muck... and by the way, diesel is a good lubricant too, just in case you still feel its needed.