Big brain time: why would aliens even come here? Would we care ourselves to send ships that cant communicate back because of time and distance? Whats the point really?
Various reasons:
1. A scientific study of us, as an intelligent race. In this scenario let's say they've been observing a couple centuries.
2. Life seeded. They engineered us, maybe partly in their own image, maybe not. Why? Unknown. Because they could? Because there's a valid super-science reason beyond our comprehension? We are an uplift/exultation experiment. In this case, they've always been here from our perspective.
3. Resources. Basically Earth has something they want or need- maybe it's us. This can be as simple as ore, water, or gas or more esoteric. Think "spiritual", if DeLonge, Vallee, & Davis are to be believed. Note this isn't mutually exclusive from the others, in particular #2.
4. They're not extraterrestrial, they've always been on earth and this isn't a matter of traveling.
And obviously these answers all work regardless if they turn out to be interdimensional beings or not.