In the way I positioned my DIR-855, it is impossible view the LCD and also to navigate the menu using the buttons without physically jostling the router and in the process, disrupting the wireless signals.
But for setup, having an LCD to display and/or having buttons with which to configure to an initial IP address would be helpful. A device with a default static IP address, 192.168.0.50, isn't convenient when there is no wired client. Neither is acquiring a DHCP IP address universally convenient for all networks. The LCD and buttons already exist. Question is whether D-Link has resources to implement, debug, and support extended functionality over the lifetime of the product, while offering a solid product to customers at an attractive price. I would guess that the LCD would break down before the rest of the unit, so being able to operate without one should be primal.
For setup, it would be convenient to continuously display the signal strength or SNR values and/or packet statistics for connected wireless clients, to aid instant positioning of the router and/or antennas. Showing details for a single client may be helpful for some situations, but displaying results for all connected clients can help in situations where the router must be optimized to serve multiple clients. Having the display on the router is easier to monitor, than say viewing the client info table on a laptop. For if the laptop is tethered to Ethernet, then it isn't a portable monitor, while if it is connected via wireless, then movement of the laptop may alter the wireless signal environment.