First - it is social dancing. You have three minute conversions with your dance partner and there are no words. When the dance is over you leave with the one who brung ya. If you are going to do something do it well. Consider the bonus of better balance, tone, core strength, and improved brain function as a side benefit. That's the short version, rambling soap box version follows.
I started ballroom in my early 20s and I was geek/nerd version #1. Fortuitously I started with group classes and did not start private lessons until months later. In group classes the partners are rotated and for a long time I did not have to ask for a dance. In the group class environment you learn to lead/follow better/faster. I did not start private lessons until months later. Then at the parties at the same ballroom I was familiar with the women and it was easier to ask. Then later when I got married my wife was OK with the ballroom dancing but insisted that I always change partners - hence my lead skills were always improving.
I manage a ballroom club and there are couples who don't rotate. If they social dance at all they only do the figures from the class - there is no lead-follow; they are familiar with each other and the leader can be less clear. I am not saying they is not OK for them, just understand the limitations. Here is where that goes south: say the un-rotating couple go the inevitable wedding, company party, maybe New Year's dance. The couple dance together well to the unfamiliar eye. The woman's friend says "your husband is such a good dancer, can I have one dance with him". The women beams and loans the husband out. What happens next is a disaster, he has rarely danced with another woman and doesn't really know how to lead, no matter the skill of the friend.
Again - not rotating and always dancing with your SO is OK if that's what you want, but it is limiting.
And I know some with think I am exaggerating, I am not. I have been involved in ballroom for a long time, I have observed 100s if not 1000s of men at dozens of ballrooms. Most men even if they stick with dancing for years stop improving at a little above average (I know my use of average here is statistically skewed but go with it) because at at that level they don't pull on the woman's arms and are more likely to dance with their body. Since women out-number men most of the time they rarely are told no when asking for a dance. I quote an advanced instructor whose class I attended: "Let me show you how to lead this, now I know you think you can lead, but you cannot, you are only better than the chair". Women just want to dance and the little-above-average guy is better than the chair.
