Isn't a 125cc one of the steps in licensing in other, more advanced markets than ours? 
It starts at $5000 USD...for a 125!
You're right Hawk. Here in the UK (and I believe the EU), 125cc is the upper limit for a young learner until they pass their test to move up to an A2 licence. Older riders can jump straight in to the A2 category. Here's the complex rules & regs for getting a UK full bike licence*:
AI summary - gaining a full UK bike licence
Gaining a full UK bike licence involves completing Compulsory Basic Training (CBT), passing a motorcycle theory test, and passing two practical tests (Module 1 and Module 2). Riders aged 24+ can take the Direct Access Scheme (DAS) for an unrestricted license, while younger riders (17-23) follow staged routes (A1/A2) based on age.
Step-by-Step Process to a Full Licence
CBT (Compulsory Basic Training): Mandatory one-day course to enable riding a 125cc bike with L-plates.
Motorcycle Theory Test: A specific test for bike riders (separate from car theory) required before practical tests.
Module 1 Practical Test (Off-road): Manoeuvres in a safe, controlled site (slalom, U-turn, emergency stop, etc.).
Module 2 Practical Test (On-road): A 40-minute road riding test covering traffic, speed, and hazard perception.
Licence Categories by Age
Age 17-18 (A1 License): Light motorcycles up to 11kW.
Age 19-23 (A2 License): Medium motorcycles up to 35kW.
Age 24+ (DAS - Category A): Unrestricted, full power motorcycles.
Key Information
DAS (Direct Access): The fastest way for those 24+ to ride any size bike by training on a 600cc+ machine.
Validity: A CBT certificate is valid for two years.
Test Machine Requirements: Module 1 & 2 must be taken on a bike with at least 595cc and a minimum power output of 53.6 bhp for a full DAS license.
Training: While not strictly mandatory, professional training from schools is highly recommended to pass the modules.
* Back in my day (1968), learners could ride up to 250cc bikes with one test to shed number plates which then entitled you to ride any capacity bike and carry a pillion. My test took 20 minutes and a full two thirds of it took place out of the sight of the examiner who stood by the roadside outside the test centre! How I survived that first year post-test is still a source of amazement to me.