People need to understand the concept of "celeb halo".
To normal people, Shakira's attractiveness multiplies by 100 because she's a world famous performer but in the celebrity bubble of Pique and Shakira's life you see it as "yeah, she's my partner" not like "Wow! I can't believe I'm with THE Shakira", hence we need to look at this from Pique's perspective instead of an outsider's one.
Also, there are plenty of sexier women out there who look much better than Shakira but they don't have status halo she has. They might make life way more fun for you than a Shakira does.
At the end of the day, in marital life, you don't care if you're wife is super-famous. What matters is if the relationship is working. All those "Power-Couple" things are PR guff; only good for grabbing headlines. Tell me how many of them are actually happy behind the dichotomy of fame!