Maps 10' grid... WHY?

So was going to run some old school campaigns and decided on running the lost city, and see that they made an upgraded version for 5e in Quest from the infinite staircase, which also had Pharaoh another old school campaign I wanted to run so I bought it.. Turns out all the maps are in 10' grid. Everything in 5e is based on 5' so why the hell did you guys make in in 10"? 

Any chance of fixing this or adding in a 5' grid overlay in maps?  

I'd imagine it's because B4 The Lost City maps were in 10' squares.

Quote from Perringaiden >>

I'd imagine it's because B4 The Lost City maps were in 10' squares.

 The lost City was also AD&D rules and they managed to update it to 5E but didnt update the maps to go along with it? yeah thats not a good excuse for anything