Bathroom fan vented in the loft

Cowboy alert

Pouring damp air straight into the loft isn't going to be good for the wood holding your roof up. If he's pointing it through the floorboards that's even worse, it'll rot there in record time. It needs to go out through a hole and have no kinks where water can pool up. There also needs to be a way for the condensation in the pipe to drain away otherwise half the moisture goes straight back (and damages the fan over time).

Why cant it be done through the wall, because he couldn't be bothered with drilling the hole ?

I have seen it before with flex/static ducting that vents to behind where the soffit boards to a house are.. I should imagine this is only done where there is no external wall. If there is an external wall then it is just lazy or there is some sort of building regulation due to proximity to next door or a window etc.

You should really post a photo of the loft.

(edited)

Venting the bathroom extract directly into your loft is a bad move....condensation, damp, potential rot of the woodwork depending how long this goes on for.
You might be able to get a soffit vent as someone else has mentioned and then route the flexible hose into that which would vent it to atmosphere outside the property....but that depends how much room you've got where the roof rafters extend at the external wall.
To put an extract to an external wall from the bathroom would have meant using a diamond core bit to drill a hole all the way through....which is a lot of work and drilling dust hence why it was far, far easier to drill a hole through some plasterboard into the loft. But it's not acceptable to leave it venting into the loft.

Where did he park his horse when he came round to fit the extractor fan?

Oh & the reason it vents to the loft is they don't want to pay to retile the bathroom. Which is fair enough.

Yes, laziness - you also don't have to drill through the wall - it can be vented out the eves - less effort

Should've been another hole in da wall or one less brick in da wall.

Me thinkin, going through the roof is much worst than going through the wall, think water ingress, thermal bridging, pigeon shi ting, bird nesting, flashing and counter-flashing, Mary Poppins, ....... (edited)

Ironic that you have to undertake a ventilation task before you can have insulation work done!

"In bathrooms with baths and showers, mechanical ventilation is required in the form of an extractor fan. This is because new-builds these days are built to be more airtight, so natural ventilation is much lower. The ventilation requirements for a bathroom extractor fan is 15 litres per second/ 54m3 per hour."

There are options to venting - through a loft is a useful option if loft is used only as storage and not habitable space but must be vented through the roof via an air vent / vent tile (not open in loft space). Through the wall wouldn't be an issue from the pictures uploaded - isn't difficult but you have to core drill through your tile/brickwork / cavity which is labour intensive and not a 5 min job! Whilst i'm familiar with building work - you could ask an established handy-man to do for next to nothing where as ask a builder and its "hundreds" more... The issue perhaps is the electric supply to the unit - as its attached to the ceiling the cable will be connected in the loft to existing supply where as on the wall the cable has to go in the cavity and access is limited and more open to making a mess of the room to then make good at cost.

Useful points made here (says toilet):
Is it a Legal Requirement to Have an Extractor Fan in a Toilet? (atspaceltd.co.uk)

cheaper to cut soffit and vent that way forget coring holes too much work u need massive amounts of steam daily for long time to cause any problems even better you have window already for ventilation