There is no metabolic pathway that converts lipids to glucose. Your body will not be able to metabolize glucose from your diet if you're eating only fats.

The metabolic pathways which do produce glucose are:

1) Eat starches.

2) Eat protein.

Starches are converted directly to glucose. Protein can be converted to glucose by a process called gluconeogensis. This is what happens under either a starvation situation (in which case the protein is supplied from body tissues -- skeletal muscle and eventually organ tissue), or under a ketogenic diet, in which dietary protein could be utilized.

While dietary glucose is apparently not necessary, it's also not a bad thing, provided you're not getting excessive quantities or low-fiber sources which trigger an excessive insulin response.

That said: the typical Western diet provides more than ample glucose and starches, often in an overly refined form. That can trigger lipogenesis, in which excessive glucose is converted to lipids and stored as fat.