To make your new Stellar account activated, you need to have at least 1 XLM on it.
This rule is forced by Stellar network (not Lobstr) and you can read more about it here:
Certain exchanges and wallets will not send transactions to inactive accounts (with zero lumens balance), which can be confusing for new users and make initial funds receiving more complicated.
To make things easier for you, LOBSTR provides you 1.5 XLM credit to activate your Stellar account at its creation moment.
You'll need to return the 1.5 XLM credit after you will deposit more lumens to your account.
Until 1.5 XLM credit is paid off to LOBSTR, you'll not be able to see your secret key.
If your account is inactive for more than 30 days, it may be deleted by LOBSTR to return the credit. You will receive multiple email warnings in advance.
If you do not want to receive 1.5 XLM credit, you can always generate key pair for a new account on Stellar Account Viewer (Click "Generate" button). These keys can be imported into LOBSTR but your account will be inactive and will need to be activated with minimal 1 XLM payment.