I felt that way at first when I started going. If it's one thing I learned since meeting my husband is engineers love talking to other engineers about engineering lol. So you tend to feel left out when that occurs no matter the scenery.
But in the end there's normally
something in common with the significant other or at least exchanging pleasantries about mundane things can occur (though small talk isn't everyone's thing to do in the first place). Many of the actual employees end up talking about work-related stuff anyways so sometimes that's the in common thing like 'oh yeah my husband/boyfriend/wife/girlfriend/whatever worked on that project too' or 'oh yeah I heard about that project' or 'did X have to go on site?', etc. Otherwise a lot of what we end up talking about is family life, things about our metro area, home projects one may be doing, etc. But I totally understand how you feel