Yes, a wooden street bench placed directly on soil will almost certainly attract termites and rot faster than one kept off the ground. The main reason is constant moisture. Soil holds water after rain or watering, and that moisture wicks up into the wood through the legs or bottom rails. Rot fungi need sustained moisture to grow, and ground contact gives them exactly that. Even naturally durable woods like cedar or teak will eventually break down when sitting in damp soil for months or years.
Termites are also a serious concern. Subterranean termites live in soil and travel through mud tubes to find wood. A bench leg pressed into the ground is like a direct highway for them. The wood stays damp and easy to chew, and the termites never have to expose themselves to open air. Even if the wood is pressure-treated, the cut ends or areas where the treatment has worn thin can still be attacked.
That said, you can slow down both rot and termite damage with a few simple steps. First, raise the bench so no wood touches soil. Use concrete pavers, bricks, or metal feet under each leg. A gap of even one or two inches helps a lot. Second, seal or paint all cut ends and the bottom few inches of the legs with a wood preservative or exterior paint. Third, if you must place the bench directly on the ground, choose a wood species with high natural resistance, like black locust, white oak, or tropical hardwoods like ipe. Keep an eye out for mud tubes or soft, spongy wood near the base.
In short, you should not set a regular wooden street bench directly on soil if you want it to last. The combination of moisture and easy termite access will shorten its life dramatically. Elevate it, treat the wood, and check it once or twice a year. That way you keep the bench attractive and safe for years to come.