Is it possible to deploy project using WMDeployer Package built in services?
Yes it is possible. Deployer is using those services only.
Just one thing, removing service dependency using built in service is bit tricky as input is generated at run-time.
Any specific reason to use services instead of WmDeployer UI?
Yes… I would also suggest to use WmDeployer UI out-of-box rather than calling deployer* service programmatically and its a unnecessary over head.