I think the issue landscape architects face most when discussing our field with people not from design backgrounds, is a lack of understanding of the range of scales. Most of my friends and family that aren’t in a design field are only aware of the designed landscape at the residential scale of a garden or a backyard. Maybe this is due to the popularity of shows on HGTV about “doing backyards” or garden design, and the term “landscape” makes them automatically associate LA with the practice of landscape design. But as with architecture, I think what distinguishes LA from landscape design is the potential to design at an extremely broad range of scales. Someone might just not be aware that landscape architectural projects can take place across so many scales. These can include projects at the scale of the backyard, all the way up to a city or region.
Landscape is such an ambiguous term, so I don’t think every LA should automatically pretend to love designing at all scales. Nor should anyone feel obliged to take on a project just because it’s a landscape or to be polite. We all have different preferences for projects we’d rather work on, just as architects may prefer to specialize in detailing a threshold, designing a residence, a skyscraper, or an entire city.
I think your response to “can you do my backyard” should depend on your own openness to working at that specific scale. Every LA is entitled to have his or her own preference.