Why processing time takes so long for spouse visa outside UK

[XJ2011]

I have ILR and my husband is going to apply for spouse visa outside of UK. I checked the processing time of the local visa application center and it seems this type of settlement visa will normally between 40 to 80 days ! at least 2 months to get the result.

Why it takes so long? Compare to other type of visa, this is a bit more to check but still not explained why it can take so long to process. I am curious, is the decision made by the casework in the local office or actually they send the paper to UKBA to make the decision?
Anyone knows?

[Lucapooka]

I am curious, is the decision made by the casework in the local office or actually they send the paper to UKBA to make the decision?

A combination of both and depending on the location where the application is submitted. Most applications are now being sent to regional hubs. However, that, itself, is not a delaying factor. The length of the process may depend on the volume of applications and what relevant checks on the background of the applicant (especially in the case of those that have previous immigration history wrt the UK). These checks may need to be conducted with agencies in the UK and the EC Hub has to wait for the results.