The fist service for the big four is free i.e. there's no labour charge you just pay for the oil, other manufactures can and do make you pay.
That's said not having a first or any stealer service doesn't stop you claiming against your warranty should the bike develop a manufacturing fault in the first 12, 24, 36 months or whatever warranty period they give you. Remember warranty is for the bike failing due to faulty parts, not parts that have failed due to misuse or lack of maintenance, reasonable care or length of use all are easy to identify, e.g. after 3k your chain breaks it's inspected it's found to be corroded, excessively stretched with kinked links clearly not been cared for so not a warranty claim.
These so called warranties are really only what the law requires i.e. the product must be fit for purpose the manufactures just offer extensions. If your bike suffers some kind of failure due to a defective part/s during the warranty period who changed the oil has no bearing on it the part/component failing, providing the bike has been serviced using quality parts/oil to the manufactures standards.
In fact the manufacture has to prove the bike hasn't been serviced correctly to reject a claim, what you will find is it's not the manufacturer/importer who mucks you about but the franchised stealer. A stealer is only paid a flat rate for warranty work as laid down by the factory so if it takes 30mins to change a part that's what they get paid and no more, regardless if it takes longer. It's all down to margin, money and through put, if a stealer is doing warranty work this takes up workshop time which he can't charge you anymore for. Sadly we all know there are a lot of money grabbing stealers out there, some are just downright dishonest! There are many well know examples of their tricks the most well known is, bike in for a service and low and behold they find this and that wrong with it i.e. extras which they can charge you for. That way they are maxing their workshop time on your bike to make money, often this work isn't needed the dishonest one's don’t even do the work but charge you anyway!
There are many who try and refuse to do warranty work for the reasons given above or that they didn't sell you the bike, they don’t regularly service it and wont see it again i.e. they have earned nothing from it nor will they. In these cases all importers have there fall back dealers who they will end up sending you to if you have trouble. This often happens with recalls i.e. the bike is outside of warranty and there's a fault. Last one I can think of was GSXR's master cylinders all 1000/750/600 built since 04 I think it was, had to have their master cylinders replaced, importers do a deal with a few large stealers and they do all the work.
I've had 30 plus bikes over the years the vast majority of those have never seen a stealer workshop from the day it left their shop, not even the first service, I've had several warranty jobs done over the years without issues to name a few:-
RD350LC 4LO carb mods and exhaust flanges.
GPZ900R camshaft oil spray bars.
GSXR1100 repalcement cylinder block and pistons.
ZX10 front pads and discs
Hayabusa fuel return pipe, and sub frame.
None of these bikes had been serviced by stearlers all by me.
If your bike has been properly serviced, it doesn't matter who services it providing it's serviced as per the schedule with quality parts/materials, manufactures can't refuse to honour warranties.