Why France Build's SSNs only for itself and Only Exports Diesel-Electric & AIP Subs

Partly utilising the wonders of Google AI Pete has created:

Question: Why does France only use SSNs for itself while only making diesel electric submarines for export?

Answer: Based on the sweat of millions of writers (and I don't get paid - just patriotism :) comes:

France uses nuclear-powered attack submarines (SSNs) for its own navy because it requires global reach and continuous strategic deterrence, but it exports diesel-electric submarines because strict non-proliferation laws, high costs, and low buyer demand make nuclear exports impractical. [1, 2, 3, 4]

1 is https://www.nti.org/analysis/articles/france-submarine-capabilities/

Why France Uses SSNs

Global Operations: France has overseas territories and global defense commitments. Nuclear subs can travel fast and far without ever needing to surface.

Carrier Strike Group Support: French SSNs protect the Charles de Gaulle nuclear aircraft carrier, matching its high sustained speeds. It can do at least 27 knots - see right sidebar.

Strategic Doctrine: France treats nuclear propulsion as a vital, sovereign military secret tied directly to national safety. [1, 2, 3, 4]
On top of SSNs France cannot afford diesel-electric+AIP subs for itself. In any case, there are sufficient supportive NATO allies (Germany, Italy now Sweden and eventually Norway and Poland) with AIP for shorter range sea missions - mainly against Russia.

• [Pete comment: Only SSNs can reliably defend France's SSBNs from Russian SSNs and Russian fast surface ships - particularly when French SSBNs are leaving-entering France's SSBN base at Île Longue (Long Island), Brest, Brittany, western French coast.] 

An excellent Indian In Our Defence video (here and above). Interviewee explains the differences between Diesel-Electric+AIP and Nuclear powered submarines. (Accents not too heavy for me - but please also use the "Subtitles/Closed captions" thingy second to the left on the right-lower corner of the video image).

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Why France Only Exports Diesel-Electric + Rarely AIP add-on Submarines

• Non-Proliferation Rules: Exporting naval nuclear reactors risks spreading sensitive technology that can be weaponized. [And France would get blamed as the original reactor source. Hence France claims Brazil is only developing an indigenous Brazilian submarine reactor. A fine line.]
  
  
Market Demand: Most nations only need coastal or regional defence submarines. Diesel-electric boats (like the Scorpène-class) are quieter in shallow water, much cheaper to buy, and cheaper to run. 
Buyer Constraints: Most countries lack the specialized nuclear infrastructure, legal frameworks, and trained personnel required to safely operate and refuel nuclear reactors. [1]

 Pete Comment

After France developed first generation MESMA AIP (with Pakistan the only customer) France has not fully developed second or third generation AIP at sea operationally. Part of this may be development cost, India resenting any more French AIP for Pakistan. competition too high from Sweden’s Stirling and German PEM AIP. Also France’s Scorpene customers (Chile, Malaysia, Brazil and eventually Indonesia) get more benefit from batteries. Whether India’s Kalvari Scorpenes will ever be retrofitted with AIP is an open question.  

About larger French designed subs for the terminated Australian Shortfin/Attack class and the Netherlands' continuing Orka Program - they did not want AIP. This is because their long range/high speed transit mission profiles gained/gain little or nothing from heavy liquid oxygen (LOX) AIP technology after the LOX is used up. 

Unsurprisingly there is no standard power mix solution for submarine exporters' own needs and their customers' needs. It depends on their mission needs, geography, cost and many other factors.