Everyone here is assuming a functional company with proper access control rules and answering accordingly. That is not guaranteed.
The other answers are correct on the following points:
Permissions granted should not be a proxy for status/rank.
Permissions should be granted based on job needs, not seniority.
Permissions should be granted minimally, i.e. you should only need read access to understand the production environment.
Different teams may have different permission needs. In my job, I don't have production DB access. People on other projects do.
Notice my use of the word "should." The fact that your manager is seemingly willing to give you all permissions (or at least never made the distinction in your discussion between read and write with him) makes me wonder whether any of that matters.
It is difficult for us outsiders to peel apart whether permissions are actually a status thing at this company. A friend worked at a company where anyone the boss trusted was often given the admin password to their computer so they didn't have to call IT. That wasn't planned security, just a sign of favoritism.
In one of my jobs, there were long passwords to make it seem like security was taken seriously, but they were kept in a plaintext file on the Google Drive for anyone to use. People who had their access restricted to that file had been moved from trusted to not trusted.
A person I met at a hackathon had a company where passwords were sent via FB. Whether you got admin rights to the server or not depended on whether the boss thought your personal FB password was secure.
If others on your team who do the same work have the access permissions you are seeking, then it could very well be a trust issue. If not, then it is probably a permissions management issue.
If it is a trust issue, you should probably depart because their threshold to trust seems low if a junior guy gets full permissions in a week.