I would suppose that it depends on the agent.
A quick look at the Hays travel website gives conflicting answers:
For Holiday travellers:
'Visa requirements vary from country to country. For information on passport/visa requirements and other general travel requirements, please visit
www.gov.uk/browse/abroad. Please note, it is your responsibility to make sure you have the correct documentation to allow entry, and travel to and from, the country you are visiting.'
But on their Business travel area:
'We can assist you in obtaining entry visas to over 200 countries and electronic visas like an Australian ETA or a US ESTA. We also provide UK passport renewal as well as other documents, such as letters of invitation, legislation and document translation. With Passports & Visas we have the experience and global network necessary to effectively reduce the time associated with obtaining travel documents and legislation'.
On your recent cruise you were 'only' a holidaymaker, so it is likely they just sell you the tickets and everything else is your problem.
Maybe the smaller independant Agents would give a more personal service, but you woud likely pay more for it.