There are some people who lean this way and that's fine - there's nothing wrong with it - but there are other people who don't. This will tend to follow an age distinction (with older folks being less interested in having more personal/professional crossover) but I strongly disagree with it being generational.

Your team at work will change over time and new people will join and leave, as you are forced to reconcile changes of employment with the destruction of your social circle I think you'll find that it's easier to move to keeping the two separate. Having children and a strong life partner can also contribute to this - there are a lot of relationships you care deeply about outside of the workplace and you don't want your time at work to be complicated by drama from the fact that you don't value your relationships with your coworker over that of your partner.

Social events at work can be fun and build a stronger team, but viewing your coworkers as your primary social circle probably isn't a healthy long term choice since at some point that relationship will be severed (hope that you don't have to fire a bestie) and someone will be left in an emotional lurch without a shoulder to cry on. I've found it quite helpful to be able to empathize with coworkers and chat about what's going on with work bits in a more safe environment but going into work hoping to find good relationships (social or romantic) is placing a large burden on those you're working with and can end pretty terribly.

I'd also point out that strong social bonds are a reciprocal thing and that while you may be entering the workplace hoping to form those bonds your coworkers may not and the visible existence of cliques in work that exclude some employees that may simply be uninterested in such social activity can lead just as easily to drama in the workplace.