It's not unheard of. But I guess it's a mix of several small factors:

1. divorce rates have been rising for decades.

2. 60 years is a very long time, and that means Dolly would have had to marry around 18-20. Marrying that young these days for my generation very much is an anomaly, and people are putting off marriage more and more these days.

3. Celebrity culture in particular has a much more tumultuous relationship. In a number of cases, marriage may simply be another influential tool to manage fame and wealth rather than an act of love and caring.