It can also depend on how many developers will write with your framework, and how long your code is expected to live.
If the code is built on a custom in-house framework, you are putting the burden on everybody to learn it and understand it and hope they can see it the way that you can. No one will really be as invested as you in understanding the ins and outs of the framework, or the special features you added that they won't even think is available, and won't care to discover or ask about.
With a well known popular framework, not only is it likely to have more documentation available online, there will be more resources from other people blogging about solutions, workarounds, tips and tricks. There will be additional libraries built on top of the framework for common problems. There is the incentive that getting good with the framework can help them in their next project or their next job interview. Lastly, it also reduces the friction of adding new team members.
If the code is built on a custom in-house framework, you are putting the burden on everybody to learn it and understand it and hope they can see it the way that you can. No one will really be as invested as you in understanding the ins and outs of the framework, or the special features you added that they won't even think is available, and won't care to discover or ask about.
With a well known popular framework, not only is it likely to have more documentation available online, there will be more resources from other people blogging about solutions, workarounds, tips and tricks. There will be additional libraries built on top of the framework for common problems. There is the incentive that getting good with the framework can help them in their next project or their next job interview. Lastly, it also reduces the friction of adding new team members.