Would you move into an apartment before checking if it's actually for rent? Would you pull into a parking space that's not empty? Would you put on a pair of underwear before making sure that someone else isn't already wearing them? No, you'd probably check to see whether any of these things were available first.
So why not do the same before even considering a romantic relationship with someone? This may seem obvious at first glance unless Ashley Madison or Adult Friend Finder happens to be your dating site of choice. And for most people, "show up" is an important requirement for a date to be successful.
But physically available doesn't necessarily mean actually romantically available. In fact, being willing to date you doesn't necessarily mean being romantically available. Heck, even someone who's already your significant other may not be romantically available no matter how close you may seem. The other person may think or insist that he or she is romantically available but really isn't. I once dated a woman whom I'll call Reallyluvs Someoneelse.
When I first met Reallyluvs, she was already longtime friends with a guy, whom I'll call, Doesntluv Herback. At some point long before I had met her, Reallyluvs had expressed romantic feelings for Doesntluv, but take a wild guess as to how he reacted to her? He just wanted to be friends. Early on during our relationship, Reallyluvs told me that her previous beau had been jealous of the time that she had continued to spend with Doesntluv.
Perhaps she was checking to see how I would react. My frank response at the time was that I had no problem with her being friends with other guys. But it soon became apparent that Doesntluv was always her number-one priority.
