I think I will wait for actual conformation and solid facts and tests before I wet myself with excitement. As it would be such an important discovery it is still best to wait for actual proof, rather jumping to conclusions with "perhaps", "possibly", "could indicate" proof (especially when hyped-up and distorted by the media).
I'm a little cynical about claims of life on Mars.
I don't subscribe to conspiracy theories, but note where the vested interests lie.
If a reasonable suspicion can be raised that life exists on Mars, NASA's budget problems are over.
Any academic who can raise a good sounding argument for this is assured of substantial publicity which will do more for his academic career than a hundred papers published.
Then you get the anti religious and UFO types who feel they can use this to make ground.
Throughout, the press will sensationalize even a hint of sucess, whether properly backed up or not.
Generally, people want to believe there is life "out there".
With so many vested interests, we need to be very careful to thoroughly vet such claims before giving vent to the natural excitement which such a (substantiated) find will give.
My feeling is we are far more likely to have convincing sounding false calims than genuine, verifiable findings.
Actually, NASA is not making any such claim. It's only that, in the absence of volcanic activity, there has been no known (historical) explanation of the methane release. Until such a mechanism (if any) is found, there is no valid reason for (or good science merit in) dismissing the known connection between microbes and subsurface water as a possible explanation...and no reason not to further explore to see if the life-form hypothesis possibly holds.
But, I do agree with the essence of your statement: that pursuit of "life" (forms) on alien worlds is, for the most part, not much more that justification (for unenlightened public consumption...of hyped "news" reporting) for continuing projects (read, public funding) in the face of increasing skepticism as to the comparative value of space exploration. Really not much different than tricks used any public, or private, budgeting endeavor.