Breville machine question?

I am looking into upgrading and buying a Breville espresso machine. I am really over drip coffee, french press, and currently feeding my latte addiction through my Nespresso Vertuo but i want to have 2-3 coffees a day, it adds up too much on pods and I don't use all of the pod options the machine offers.

In terms of budget, I am in the $500-$600 range. i have seen a ton of suggestions on this thread about the Barista Express, which a friend of mine has and loves. I just am having trouble justifying the $700 price tag but what I have noticed on here is that for those that opt in for a different machine, such as the Duo Temp Pro or the Bambino, people kept suggesting a burr grinder. If i go the Duo Pro and a nice grinder, i'd be spending that much anyway..

So.. this is coming from someone who just enjoys the taste of a latte and or something of the like, so pardon my ignorance. But what is the benefit of purchasing a burr grinder instead of getting espresso beans already ground up? Does this purely just enhance the experience? Should i just buy the Barista Express?

For those of you that have Breville machines and don't use a burr grinder, do you still enjoy the machine?