The first reason is that installing software is complicated.

At that time, when the system became popular, there were also many pirated applications. In addition, unlike the software we download now, there is no dedicated software application store in the mobile phone. If users want to download, they must download online. At that time, the Symbian system introduced a signature mechanism to prevent malicious programs from entering and reducing the smoothness of the system. A signature mechanism must be used to download software, and only signed applications can be installed on the phone. The whole process is very complicated, and many users do not know how to sign at all, so the experience is very poor, which causes users to dislike this system very much.

The second reason is ecological decline.

At first, Nokia was not the only mobile phone brand using the system. Sony Ericsson and Samsung both used Symbian systems at the time. However, for some reason, Nokia withdrew the authorization. In other words, no other phone brand can use Symbian's system. Only Nokia's own phones can use the system. In order to understand the ecosystem of a system, even software developers have to develop it. At first, there were still many brands available for the system, and the number of users was relatively large. For developers, it also feels like it has greater market value. However, after using just one brand, developers found it of little value. They did not pay attention to this, and the natural ecological chain began to gradually decline.

The third reason is the high threshold for software development.

Due to the withdrawal of authorization and the use of only one brand, the ecological chain of the system is gradually declining. In fact, this is just a point. Another point is that the system's software development threshold is too high, which requires developers to handle memory allocation and response function module operations. In short, the software must consider the use of multiple phones, such as keyboard phones, touch screen phones, etc. and the software resolution displayed on the mobile phone, so development is relatively difficult.

It happens that the Android system solves this problem very well, which is why the Android system can easily occupy the mobile phone market later.