City apartments lose favour with buy-to-let investors?

City centre apartments and buy-to-let were once so closely linked that many developers openly marketed directly to investors. The city centre apartment holds a lot of advantages for the property investors, they have no exterior maintenance to organise. The properties are modern and popular with tenants.
So why have these lost favour, the main reason is simple cold hard cash, the rental yields that could be achieved have never been great but property investors weighed this against the many other advantages. Rental yield have not really improved as there has been downward pressure on rents, but even more concerning is that the capital values have dropped since the UK housing market peak. Most property has suffered capital losses but new build city centre apartments have been the some of the worst affected. However there are now signs of larger cash rich investors making bulk buys of these properties as they look to the midterm and some potentially large gains