You make a good point. I extended the plus one option to all my guests and some people invited random people I’ll never see again. But I viewed it as a way to respect my friends who I did want very much to be there. I figure if you’re going to throw a big wedding, then give guests the options to bring a date/friend.
One of my old bosses actually brought her son as her plus one, the only kid under 10 who came (my cousins were all teens or older). You can clearly hear his voice on the wedding video saying, “I’m hungry, Mommy!” right before the welcome speech. I still laugh at that memory!