As said, it's just image.
No, it's not. See below.
Why is it a 'problem' to use a .uk.com domain name for a UK based company, rather than .co.uk or .com.
In a nutshell.
UK.COM is not a TLD.
UK.COM is a .COM domain name owned by Centralnic (amongst other similar ones). So when you acquire a UK.COM domain name, you are effectively obtaining rights to use a sub-domain of UK.COM.
In contrast, where you to obtain a .COM,.UK etc. domain name, then you are obtaining rights to use a name from an ICANN registry (other other similar independent establishment such as Nominet for the UK).
Doing the latter rather than the former, you'll likely find the terms & conditions are fairer (particularly in the case of .UK Nominet based names.... they do a great job of running the UK registry !).