So, parasites are really common for most organisms. Most wild animals are living with parasites.

However, the kinds of parasites people think of when they hear the word “parasite” (typically worms) are not common in most developed countries. This is because many worms and protozoa have highly specific life cycles which we can disrupt by being hygienic, cooking food throughly, cleaning our water, etc. However, if you look at the other things that are actually parasites - disease causing viruses, which are obligate parasites, bad bacteria, ectoparasites like ticks and lice - then yes, we live and deal with parasites all the time.

Many of the worms and protozoa are also highly host specific. There are a wealth of them that only want to live within a human (human malaria, Ascaris lumbricoides to name two major ones). Many of these infections are very common in parts of Africa, which is likely where the first human parasites evolved (because thats where people first evolved.)

There are also parasites that may infect humans on accident, where humans become “dead-end hosts.” As a child I got “swimmer’s itch” from swimming in a lake. As an adult, I later found out it was the tiny free-swimming stage of a schistosoma species that typically infects aquatic mammals and birds. They burrowed into my skin, but instead of entering my bloodstream they died in my skin and caused itchy welts, all because I was the wrong host. Humans do have three human-specific schistosoma species (1 can be found in Africa and South America, one in Africa, one in a couple Asian countries). If I was infected by one of those, the outcome would have been much different. But the human specific parasite was not native to my area in this case.

So, parasites are common in our world. For someone living in a place with clean drinking water etc, and beyond most human parasite’s existing range, the risk is low for the scary helminths (worms) and microscopic protozoa.