Infrastructure-as-Code (IaC) enables practitioners to configure and manage software infrastructure through machinereadable code files. Various IaC tools facilitate code reuse and modularity via IaC modules that act as dependencies. These modules are maintained by IaC providers to introduce new features, resolve bugs, or address security vulnerabilities. However, there is a limited understanding of how practitioners update their IaC module dependencies in their software projects, including updates frequency, delays, as well as motivations behind such updates. To fill this gap, this paper aims to understand current update practices in IaC module dependencies, focusing on Terraform (TF), being currently one of the most popular IaC tools. In particular, we investigate (i) the frequency in which IaC practitioners update their module dependencies, (ii) the technical lag phenomena, which represents the time that the infrastructure configurations remain outdated relative to their upstream modules, and (iii) the motivations that drive these updates. To achieve these, we conduct an empirical study on 13,490 TF-related commits from 131 open-source projects. Our results reveal that only 1.2% of the analyzed commits involve updating module dependencies. Furthermore, we observe an increasing technical lag from 2021 until 2024, reaching ten months on average by 2024. Then, we conduct a qualitative study using thematic analysis on code changes involving TF module dependencies updates to investigate practitioners’ motivations behind such updates. We identify that TF practitioners revolve around six main motivations, with IaC Ecosystem Compatibility, Security Vulnerabilities Fixes, and IaC Code Quality Improvement being the three most prevalent motivations. Our findings advocate that TF practitioners need customized IaC tool support for safe module dependency updates while addressing compatibility concerns.