If you were a soldier in 1700, you were most likely a mercenary. So also in 1300, or 700, or 700 BC, and so on. When your own territory was under attack it might be all hands on deck, but even then, most of you were just cannon fodder or buffer. There were trained professionals who had the good weapons, the armor, the horses, and they were expected to carry the load. There is a long development of states in the Middle Ages refining their abilities to tax to raise money for wars, and ever-larger armies meant more and more citizens of each had some close connection to the military, current or previous, but even up until 1750, 1800, military service was not generalised in the population. The colonial experiences were an accelerant, in that many Americans participated in battle or support in some way leading up to and through the revolution, but that was still atypical. Most Frenchmen or English back in Europe did not have this. Only the peoples moving as groups, such as the Huguenots or the Scots-Irish, had generalised experience of military involvement, and this was often informal and intermittent.
Around 1800 this changed, and the change lasted until 1950 or so with the demobilisation from WWII. Since that time most places have gone back to professional armies. We didn't especially notice it in America because so many of one generation had been to a foreign war, part of a large invading force rather than the (at least potentially) defensive forces of Europe and the Far East, and we sent sizable armies to Korea and Vietnam after. It has been noted since then that the cultural expectations are different, with great swaths of the population giving little or no consideration to ever being in the military, while other sectors - southern, Hispanic, rural, western, dominating the subsequent military. (There are also difference among the various services, which I ignore for the general discussion.) There has been some wistfulness that perhaps it would be better if it were like the old days, when the army and navy included the sons - and now daughters - of everyone and we all felt more of a stake in that. The Israelis are pointed out as a good example of this, and the Scandinavians and Swiss, even though they don't go to war, have everyone take a turn in the military when young. I won't take a position on whether this would be good for us or not, I am simply noting that it was the years 1800-1950 that are historically unusual, not the norm. We think back to "the old days" and that's what we think of, but that was a particular moment in time, when nationalism and large set-piece battles were the norm, rather than skirmishes and professional armies.
We don't usually notice, in such a discussion, how much private contractors do the work of professional military these days. It's not that different than hiring Hessians - or Amorites, or Goths, or Saxons. We have returned to the practices of the even earlier eras, back in line with what has been the common experience for most of the civilised world for millennia - civilised in the sense of living in towns and cities.