Synthetics can offer advantages to the retail trader trying to mask their intentions.
If you have ever taken a position in the market and then the market suddenly moves in reverse, there are market participants that are able to cause this reaction. Even though you consider your tiny purchase to be insignificant amongst institutional traders. But every trade effects the market. So you should understand masking your intentions.
For example you may open a call (or lots of calls) but suddenly the market starts moving against you drastically, as if someone was trying to cause a loss in your account. Instead you can construct a synthetic long call by purchasing the shares and an at the money put. This is just an example, as usually more complex strategies give away your intentions.
A successful retail trader may eventually find that they are a large market participant, especially in the less liquid options market. You have to understand at this point, that large options trades are announced on TV and on newswires. You don't want to give away your intention.
Then it becomes hard to deduce if you are bullish, or bearish, or hedging an existing position, or anything else.