Why open source is needed?
People confuse open-source and free software because they think they are equivalent, and this is not so. Free software usually includes open source, although this is only sometimes the case. Don't worry; I'll make it clear now.
Why is the application free if it is not always open source? It all depends on the goals of the creator. For example, some creators of computer and mobile games do this. The same goes for open source. If the seeds are available, this does not mean that the application is free, and some licenses control this aspect. Of course, there are free, open-source applications, i.e., freedom software, and here the creators usually adhere to the Free Software Foundation's (FSF) position.
I described all this to clarify the concepts further. I will specifically talk about what open source is for, not about free and open-source software.
What are the benefits of open source?
I favor open source, as it will improve the quality of the application and increase user loyalty. I will say right away that I am not a supporter of conspiracy theories and am not afraid that someone is collecting my data. I would rather stand for honesty and openness between creator and user. It develops our society.
Teamwork is better than individual work.
A strong plus of open source is showing your work to others for evaluation. A good development process within a company usually includes a code review. That is, to write something and immediately lay it out is not good; it is better to show it to others. A person may miss or not know some points, and because of this, the work may be of poor quality. Many, it seems, understand this and use it inside teams.
The whole team can miss or not understand something; this often happens, especially when people have been working together for a long time. I have personally experienced such phenomena. Sometimes a constant influx of "fresh blood" can help, but even here, it's not so simple because an established corporate culture can interfere with change. Therefore, no matter how many newcomers you bring to the team, everything remains the same because either you join the group or leave it.
Therefore, it is much better to conduct your work openly. Show your code to public criticism, and it will be much better. This can get in the way if you need more time to be ready for criticism. The ability to accept and process complaints takes time and effort. For example, if this process is not regulated, there will be too many edits, and it will not be easy to find worthwhile ones among them. At the same time, I will warn you that if you go too far with bureaucracy, no one will help you. Well, in general, criticism processing is a separate issue; I won't go into details here.
There are examples of the effectiveness of teamwork not only in development but also in writing texts. Before it is published, even this text will be looked at by at least two people to assess whether everything is coherently written and whether there are any factual errors, and this will make this text even better.
Open work disciplines.
There is already an aspect of collective work and social pressure. If the sources are closed, then not mainly responsible developers can carelessly treat security, hoping that no one will find an error. But when everyone can see the project, it will not work; the team understands this, and the level of responsibility increases.
The same documentation will finally begin to be written; otherwise, how can an outsider understand the project? We have encountered a situation where you come to a project but there is no documentation; everything is passed on by word of mouth. Of course, this isn't good even with closed sources, but it will feel much more vital with open sources. It seems shameful to release the project into the world without writing documentation for it.
You know, it's like a kitchen in a restaurant with a transparent wall; that is, if the chef doesn't wash his hands, it won't work.
Open source builds user confidence.
When you are open to your user and tell him honestly what is going on, it certainly increases trust. I don't mind if someone collects or uses data about me, but I want to know precisely what data is being collected and when. I want to be anonymous if I create an anonymous account. Is the app's creator sure he doesn't want to harm me? I want to be sure that the application performs its functions, and I will not waste my money in vain.
Open source develops our society.
Open source has many more benefits, but I've highlighted the essential ones. The desire for teamwork, discipline and trust is a strong incentive for the development of society. At a minimum, you need to develop all of these qualities in your company's corporate culture; opening the source won't do it for you. Therefore, it is not the goal of opening source codes but the development of your business thanks to the opening of source codes.