Why not just use random_device?

I am a bit confused about the c++11 random library.

What I understand: we need two separate concepts:

• random engine (which can be pseudo (need seed) or real)
• distribution: it maps the numbers obtained from the engine to a specific interval, using a specific distribution.

What I don't understand is why not just use this:

std::random_device rd;
std::uniform_int_distribution<int> dist(1, 5);

// get random numbers with:
dist(rd);

As far as I can tell this works well.

Instead, this is what I found on most examples/sites/articles:

std::random_device rd;
std::mt19937 e{rd()}; // or std::default_random_engine e{rd()};
std::uniform_int_distribution<int> dist{1, 5};

// get random numbers with:
dist(e);

I am not talking about special use, e.g. cryptography, just your basic getting started articles.

My suspicion is because std::mt19937 (or std::default_random_engine) accepts a seed, it can be easier to debug by providing the same seed during a debug session.

Also, why not just:

std::mt19937 e{std::random_device{}()};