I think you are asking the wrong question.

Prokaryotes can function without having endomembranes.

They never 'needed' to evolve them.

Evolutionarily speaking, 'organisms' with internal membrane systems came later.

For example, mitochrondia are hypothesized to have originated by one cell 'engulfing' an ancient 'prokaryote'.

Thanks for your comment. I am just saying if they had one will that have helped them perform their functions well considering their small size.