60% enrichment is not weapons grade. Weapons grade is 80%. High enrichment is used in certain reactor designs, such as naval reactors.

There are a lot of reasons to be enriching uranium besides building nuclear weapons. Considering the US reneged on its deal to drop sanctions in exchange for Iran to not enrich uranium, it is pretty obviously useful as a bargaining chip, in the negotiations.

The US intelligence community assessed that Iran has not been working on a bomb since the program was shut down in 2003. They didn't want a nuke, they wanted an end to sanctions. They further wanted to avoid provoking exactly this sort of conflict. This did not delay them getting nuclear weapons, it will make them get nuclear weapons.

To quote an ISIS report, "Iran has no civilian use or justification for its production of 60 percent enriched uranium, particularly at the level of hundreds of kilograms". In theory it could be for naval propulsion, but experts (including IAEA inspectors) seem unconvinced.