Almost none of the Ubiquity stuff looks like that. Xiaomi has plenty of white/gray cylinders or boxes with rounded corners. TP-link has whole Deco series, Asus has ZenWifi series. Majority of MikroTik non rack mounted hardware also targets more neutral design.
You also have to consider who is the target audience for dedicated all in one wifi routers. Majority of regular people are fine with the WiFi that's builtin the modem provided by their ISP. Any serious commercial office will have the IT team to setup separate (rack mounted) router/switches and ceiling mounted access points that look like previously mentioned smoke alarms. People with large enough house to need multiple access points but aren't IT specialists willing to wire up Ethernet everywhere -> various product lines described as mesh routers. Like the trash can shaped TP link Deco series and similar from other manufacturers. If your house is not that big, nothing stops you to buy one of them and ignore the mesh functionality. That leaves people living in small enough house/apartment to be served by single router/switch/Wifi access point combo but for some reason not being satisfied what the ISP provides and also wanting multiple wired connections. Exclude the IT specialists willing to set up home lab and you are left with gamers (potentially impressed by black spider) and few others who have hopefully have enough rationality to place the router where it's not an eyesore or picking some of the previously mentioned stuff.
Another factor is move from antennas that are simple correctly size wire maybe with some spiral which easily fits in small rounded antenna to flat pcb antennas which encourage more rectangular design of the antenna housing and rest of the router. A lot of it is still partially just for the show, trying to give the impression "this one has more/bigger antennas must be better WiFi", but oversized partially empty plastic antenna housing were a thing even before current spider trend.
White slightly rounded 8 legged spider still looks like spider. Trash cans have a bunch of antennas but they hide them in larger volume. Dedicated access points have the advantage of being placed more predictably (near ceiling with little obstacles), they also have advantage of being distributed less work for each of them instead of single router covering whole house.
Somehow ordinary non tech consumers got it into their heads that something which looks like a f117 with many spiky antennas sticking out of it must be faster.
I have a U7 Lite and it is very directional compared to other routers I have used (spider style, trash can style, etc.)
Personally, I find it better to have multiple low end access points (like the TP-Link Archer C80 which has 3x3 MIMO on 5 GHz) deployed to achieve excellent coverage in a house. Sadly, the U7 line is a bit too expensive for that. Plus, I'm loathe to deal with UniFi deployments now that I am well versed in the glass jaws in the platform.
There really is space in the market for a product line that is basically what UniFi is, but done "right". Ie: can be debugged or you can fix it without an internet connection or recover the system when the owner forgets the password and lost access to the email account used for 2FA. UniFi is an absolute nightmare the moment anything goes even slightly wrong.
You can find older generations on eBay very inexpensively for what they are, install Ruckus Unleashed firmware on them, and operate them completely locally.
They have the best beamforming antennas in the industry and their firmware is rock solid. I'm on some very old models (2.4ghz and 5ghz only) but they work fantastically well. I'll probably upgrade to some wifi 6 models soon.
But for my uses 500-600mbps rock solid throughout my house is plenty. Anything where I want max throughput/low latency/low jitter (mainly gaming) is hardwired. For wifi I care much more about complete and consistent coverage.
As for why it needs multiple antennas, it's for MIMO and beam forming.