Yup, that is a difficult answer to give. Customarily, when listings show up on MLS, they have sufficient photos to give you a good look at the home, condo, apartment, etc. We can put up to 25 pictures per listing. However, even wit that, some agents do not include photos of entire property.
More often, on the ancillary sities such as craigslist, or Realtor.com or Zillow, etc., the listings are placed by the owner or manager, who put up even less photos.
I'm not sure if it's lack of ability to get good pictures, just too busy to give it the attention it needs, or they just want to give you an idea only and really want you to come see it, rather than just look at pics. Sometimes scrounging around the internet and looking at other sites, will show pictures from a prior listing. Other times, contacting the lister directly, can get some additional photos sent to you directly.