When does a website really need a VPS?

A website needs a VPS when its requirements consistently exceed what shared hosting can support. Common reasons include repeated CPU or memory throttling, background processing, a large database, high concurrent traffic, or software that requires custom server packages. Base the decision on measured usage and technical requirements; page-view totals alone reveal very little about server load.
Traffic spikes can sometimes be handled with caching, image optimization, a CDN, or a better shared plan. Moving an inefficient site to a larger server may hide the problem temporarily while costs continue to rise. Check slow database queries, uncached pages, scheduled tasks, plugins, and third-party requests before treating infrastructure as the only cause.
A VPS is also useful when the project needs command-line access, custom web server rules, a queue worker, a separate search service, or strict isolation between applications. Development teams may need control over deployment and logs that a shared panel cannot provide. Regulated or sensitive projects can have additional security and data-location requirements.
Choose between managed and unmanaged service honestly. An unmanaged VPS expects someone to secure, patch, monitor, and recover the server. Managed service costs more but gives the provider responsibility for defined tasks. Ask for a clear management scope, backup policy, recovery process, and upgrade path before migrating the live site.