The essential measures to keep water at bay are outside the house. Inside, I would limit the use of moisture sensitive finishings and keep any that are moisture sensitive an inch or two above floor level. That would mean no wall-to-wall carpeting, only loose rugs and no wood flooring of any kind. Instead, tiles or stone on an anti-fracture membrane. Put wall base plates on 1" of XPS; you might have to use floating walls because of the soil.

If you are only concerned about the here and now, you can put down a finish. HOWEVER If you can maybe kinda sorta in the future see yourself putting anything other than carpet or floating floor down there (ie tile) - DON'T!! We would LOVE to tile our basement floor... but to do so will be expensive and messy because the people who sold us the place 'did us a favor' and painted the floor. Now if we want to go with tile we have to strip or sand the paint off and THEN we can tile. Not something I'm excited about doing.

Built in 1990, I expect there's nothing on the exterior but a bit of cutback asphalt. So I would definitely look to interior protection. I can't comment on the products you mention. My preference is a crystalline waterproofing product. A minimum of 1" XPS adhered to the interior walls is a Building Science preference. I've used this method in the past, followed by fibreglass batts and a metal framed wall. EPS is also acceptable. But I find the following problems with this method: 1) adhering the boards to the walls can be very labour intensive on a poured wall. The irregularities in the wall may make it impossible to use adhesive. In fact, I've ended up using concrete screws and fender washers. With the boards not fully pressed onto the wall, you will get circulating air on the interior wall, which can lead to condensation, as can, the screws and washers. 2) metal framing creates a straight wall and is less messy than wood to build, but if the boards are not sealed properly, they will attract condensation. If you are using this method, it's best to use shiplap boards or seal all the joints with building tape. And be sure to put the baseplate of your metal framing on at least a 1" thick strip of XPS to prevent wicking of moisture into the wall through vapour movement or liquid water. Most recently, I've had basement walls and rim joists sprayed with closed cell foam equivalent to Code Minimum R12, then wood-framed. The clients can then choose to insulate between the studs or leave it open. You can also use crystalline waterproofing on the basement floor. Though with no water in 17 years, that may be overdoing it.

To answer your original question, when is basement waterproofing necessary? Waterproofing is necessary when there is evidence of water or excessive moisture in the basement or where there is a strong likelihood of water leaking into the basement, but it may not be necessary in all cases. My Grandfathers farm house has hand laid fieldstone walls and a dirt floor in the basement, yet it the 100+ years since the house was built there has never been any sign of water in the basement. There are many factors that effect whether or not you will get water in a basement, such as but not limited to: 1. Elevation of the structure in relation to the immediate topography. 2. Type of soil. 3. Height of average water table. 4. How the surface is graded to direct surface water flow and storm runoff. Just arbitrarily digging a trench around the footer wall to install waterproofing could introduce problems where none exist now. By example, all the soil around my grandfathers foundation has been settling for nearly 100 years so for all intents and purposes we could consider it "Undisturbed soil" and most likely at maximum compaction. If we were to dig a trench around that wall it would loosen that soil and invite surface water to seep down around the basement wall. You stated that you don't believe anyone in your neighborhood has a sump pump. That is not unusual in some regions where the terrain and soil conditions are right. I would strongly suggest you stop by your local county engineers office and ask them. They have very detailed maps of the soil and groundwater conditions and they could advise you whether or not ground water is a problem to be considered at your location, and if waterproofing is necessary at your location they can advise you as to what methods will work best. If nothing else, the county engineer is your tax dollars at work and he/she is not trying to sell you anything, whereas I have seen some slick basement waterproofing companies that would go to the Sahara desert and recommend basement waterproofing for the Pyramids if they thought they could get the contract.