They ask for a wallet address so they know where to send your coins. Asking for an address is okay. In order to get an address you will usually have to download a wallet and run it. If it's a scam there may be malware packaged inside the wallet. Generally this is not the case. Best defense against a scam is educating yourself and research.
Agree then you should avoid falling easily with the projet because of money much better to carefully study the background first before joining in airdrops. Although it is easy but that is your job to wait for payment. Then read more and learn unlimited.