Local currency?, do you mean a country's local currency or each town or state having its own currency?, Yes there are benefits of having local currency since you aren't only limited to bitcoin.
Local currency payment is instant-
For example, you're paying at a restaurant where you need instant payment rather than waiting for Bitcoin transfer (which can take up to an hour sometimes if you are unlucky)
Bitcoin on-chain transactions require times in average 10 minutes to get a first confirmation. Sometimes it is faster than 10 minutes, sometimes is much longer like 30 hours or 1 hour or longer if you use too low fee rate.
If needing a faster confirmation, use higher fee rate or consider to use off chain with Lightning network. The adoption of Lightning network is less than Bitcoin on-chain transactions but it is still an option.
Local currencies are fast in transaction compared to Bitcoin so I'm sure there are reasons people prefer both Bitcoin and local currencies (Look at a common example i presented above)
Bitcoin on-chain, Bitcoin on Lightning network, local currency and bank transfer, I think we need them all.