Wi-Fi constantly breaks
In most apartments, the signal from your Wi-Fi router is not strong enough to reach all rooms in your home, especially in those with thick walls.
Apart from your own home, most routers only use default wireless settings, which means that surrounding Wi-Fi signals are likely to cause interference, which slows down everyone's connections.
If too many devices are connected to your Wi-Fi or the router is simply running for a while, it can simply freeze, forcing you to unplug and reset your Wi-Fi all together.
Wi-Fi routers are a major security liability
Most people never even try to access their configuration and only use default settings. Hence, most people never take the time to manually install security updates.
For most routers, automated security updates are not available at all and security updates are not distributed in a timely manner, leaving your router exposed with known vulnerabilities.
As your home router is the center of your home networking, it is a hot target for anybody interested in observing your activities or stealing your files and it hardly has security measures built into it. The same is true for Wi-Fi hotspots in public places or at work.