result other than expected

Hi,
I made project based on customtkinter and pyserial and here's result of exporting requirements by pipreqs:
```
brotli==1.0.9
ConfigParser==5.3.0
cryptography==37.0.4
Cython==0.29.33
dl==0.1.0
docutils==0.18.1
Foundation==0.1.0a0.dev1
hid==1.0.5
HTMLParser==0.0.2
importlib_metadata==4.12.0
keyring==23.6.0
lockfile==0.12.2
lxml==4.9.1
monotonic==1.6
numpy==1.22.4
ordereddict==1.1
Pillow==9.4.0
protobuf==4.21.12
pyOpenSSL==23.0.0
pywin32==304
tornado==6.1
typing_extensions==4.4.0
wincertstore==0.2.1
xmlrpclib==1.0.1
zipp==3.8.0
```
Setup:
python 3.8.10
Windows 10 64bit

Steps:
- venv creation (using virtualenv),
- `pip install customtkinter pyserial`
- project creation,
- `pipreqs --encoding=utf8 .`
- creating new venv
- `pip install -r requirements.txt`
- venv activation
- `python main.py`
Result:
- `ModuleNotFoundError: No module named 'customtkinter'`

Result of `pip freeze`:
```
customtkinter==5.1.2
darkdetect==0.8.0
pyserial==3.5
```
Both export methods executed on 'just-created' venv in project directory.

Reproduce the report with Python 3.8.10 on Windows using the listed virtual-environment steps, especially `pipreqs --encoding=utf8 .` and installation from `requirements.txt`. Inspect the pipreqs entry point and dependency-detection path; done means the generated requirements include customtkinter so the recreated project runs without `ModuleNotFoundError`.

Written by the indexing model from the issue text.