It's more than just tradition. My experience is more from the petroleum exploration arena, so I'll speak it its terms.
Almost no property owner owns the mineral rights to their land, only the 'surface' rights. The mineral rights (in most cases) were seperated years ago.
Exploration for petroleum involves statistical analysis as well as physical discovery. Physical discovery used to involve guessing, based on prior performance or just a hunch, where there might be oil or gas. These days, there's a lot more technology to be applied. One method involves placing sensitive seismic instruments in a variety of locations. Then large machines called 'thumpers' are put in place to cause deliberate seismic disturbances. The effects of these disturbances and underground interference to them are measured, mapped and analysed using the instrumentation that's scattered about.
This type of physical discovery is not cheap. It consists of:
expensive instruments
expensive machines
well-paid geologists and other crew
paying landowners for use of their land.
costom analysis software
and more
The best ways for a venture like that to make money are to (a) sell the information to mineral rights owners, or (b) use the information to drill for petroleum themselves.
In case (a), making the information available at no charge is contrary to the business plan. In (b), they would need to acquire/lease the necessary mineral rights and it wouldn't pay advertise what they were looking for where.