Registry keys are created for deployments on your client machines because that's where we store the deployment steps executed by the deployment task. As indicated by CyberCitizen, this shouldn't affect your machines' performance and we do clean these up. A change was implemented for this back in Lansweeper 6.0.110. I've pasted the relevant changelog entry below.
Changed: #434948 When deploying to a Windows computer, registry keys related to previous deployments are now deleted, if they are older than 30 days