Smartphones have become an essential device in our daily life, and consumers use numerous types of apps. Among various apps, there are very few users who have never used pre-installed apps provided by default on smartphones, and its usage also accounts for a significant portion. However, previous research on the attention of these pre-installed apps has been limited and has been mainly addressed on the negative aspects. In this study, based on the streaming data of mobile apps for each user, we analyze the spillover effects of mobile device manufacturer's pre-installed apps usage on similar download (i.e., third-party) apps usage that have similar functions or belong to the same category. Furthermore, we observe how the effects differ according to the demographic characteristics of the users as well as the app categories, and provide interesting results for each case. As a result of the main analysis, overall, we found that there are positive spillover effects of pre-installed apps usage on similar third-party apps usage. This study provides major implications for revealing that pre-installed apps contribute to expanding the entire app ecosystem, including similar third-party apps.