It's often that small details that make those difference between being called from an interview and not being called. If they ask for it in the ads, and you didn't give, might show your reluctance to follow orders or they assume you're not sharp enough to read the requirements.

Say you give the reason 'waste of resource' to send your photo to them, your potential employer might have the impression that you're those lazy type who won't give the extra effort when performing the job.

But most probably the reason they need your photo is to give them a first impression of how you look. Either way, just send a photo of yours, no harm done.