If you are lucky enough to be able to afford (or be provided) with the premium services every time you fly, then I'd agree - not much value. Indeed, being involved in software for frequent flyer programs, it is true to say that one of the "headaches" some airlines have is recognising (and thus making sure they take "special" care of) customers who chose not to join their schemes and who travel fairly regularly in premium cabins.
I'm lucky that my employer allows me to use the premium cabins for long haul travel. That keeps me in the gold or above levels of one of the alliance's frequent flyer schemes. Unfortunately, that same employer doesn't put me in the front end on European or UK flights. However, when travelling short haul the gold card gets me into the shorter/quicker premium queues for checkin, gets me priority bags, blocked seats next to me if the flight is not full, gets me through the express security lanes at airports, and into the lounges that are often far more restful (and cheaper!) if I want a quick G&T than the scrummage at general departure lounge bars.
Furthermore, as a gold card holder, I've just booked a vacation travel for two to the USA where we've been able to immediately (at booking time) upgrade our cheapo paid-for economy tickets to business class for no additional charge - and this is the third time I've been able to do that this year. Now don't get me wrong - I could spend money on business class vacation travel if I wanted to, but when its as convenient to upgrade for free as it has been I'll keep that money for something else thankyou. Its not using the miles that's the the problem, its the WAY that you use them!
No doubt someone will tell me the frequent flyer perks I do value are earned at my employers expense. Yes, that's as maybe, but I won't get too stressed about that on the basis that I get precious little else in a life that regularly involves turning up at airports or getting home at stupid-o'clock and [despite the long haul business class] frequently feeling wrung out for days a trip.
A